can it be considered tallow and reused, especially if filtered?
I don’t have a butcher from whom I can beg fat scraps and I almost never purchase steaks or roasts where I might save my own scraps. I eat ground beef almost exclusively and could potentially accumulate a lot of fat.
At present I do reuse it by leaving the fat in the pan after frying burger patties and then sautering mushrooms, onion, or whatever for other meals.
I don’t see why not. You do want to refrigerate it though. Ideally, pour it into a jar and throw it in the fridge, then re-use it for cooking just as you would bacon grease ahem nectar. 
Leaving animal tissues at room temperature is a really bad idea (after two hours, the general food safety rule is to throw it out - as micro-organisms can multiply to unsafe levels and cause food poisoning). Pasteurized food is safer, but will still re-grow micro-organisms in time (due to spores as well as contamination post-pasteurization).
Edit: I just realized that last part could be mis-interpreted. As long as you refrigerate your grease, you can basically put an infinity symbol on it for the best before date.
Absolutely! I’d just strain it through a coffee filter into a mason jar and keep it in the fridge. There for whenever you need it.
Wait! You mean it’s not necessary to drink it all??? 
Has anyone actually done it? Have you saved, filtered, and refried something (like Carl’s ketoky fried chicken)? That’s what I’m aiming for.
I don’t even bother to take it out of the pan. I cook exclusively in cast iron. I leave the fat in the pan on the stove (or in the oven if I feel the need to hide it) and then use it for the next meal I cook. I’ll scrape the pan eventually if I cook something that leaves a lot of debris like pork rind coated anything. We also leave butter and bacon grease on the counter. We don’t get sick from it.
Actually, Shane, I do the very same thing you describe.
But if I were to use the fat to fry chicken, I’d want the fat to be cleaned of beef flavor and any crusty bits left on the bottom.
I don’t disagree with persons who caution against leaving food or grease out at room temp, BUT my mother never paid it any mind and neither have I. That’s many, many years of experience which has never resulted in illness. I’m not stupid about it, just not concerned in most circumstances.
The traditional way is to put it into a basin or bowl, pour boiling water on it and ensure all the fat has melted, shuv it somewhere cold to solidify, the bits you would sieve out are on the bottom side of the cold hard fat, just scrape them off and get cooking.
I don’t know that you can get the beef flavor out, so maybe just use your tallow for “country fried” steaks and mushrooms and other veggies and use something clean like lard for your chicken.
Exactly. I use the pan 3 times a day. I eat any of the fat as I go.
Or drain it off and refrigerate if you must 
Delicioso!
Heh. Believe it or not, but you’ve likely built up some resistance to many of the micro-organisms that will grow between temps of 40-127F.
The “rub” would be that if you have someone visiting with a compromised immune system, maybe not a good idea to subject them to that.
Pretty much all of us that cook with cast iron leave trace amounts of grease in the pan…most of us don’t wash them as we’re afraid of harming the seasoning of the pans.
Not sure about being reused, but it’s not tallow, it’s muscle fat. Tallow is the fat from around the kidneys, I don’t see it taking the heat needed to be used as tallow. This is the one I was buying before I found a local source for suet to render it myself, honestly I may go back to buying that. https://www.amazon.com/dp/B06WWG7P4Z/ref=sxts_kp_tr_2_a_it?pf_rd_m=ATVPDKIKX0DER&pf_rd_p=81796764025866896&pd_rd_wg=L6BPv&pf_rd_r=8KERKWGR8X18CPPJWTW6&pf_rd_s=desktop-sx-top-slot&pf_rd_t=301&pd_rd_i=B06WWG7P4Z&pd_rd_w=yNEyV&pf_rd_i=tallow&pd_rd_r=872128df-6f4f-4a7e-a78b-e8b703de6196&ie=UTF8&qid=1529441672&sr=2
You can definitely re-use it if you want, but it is not tallow as someone I think has already mentioned. Personally I have more bacon fat than I can use in addition to coconut oil so I do not re-use the fat when I cook ground beef. This afternoon I made some chicken fried in lard (skin only the ‘Butter Bob’ way), another great frying oil. We really joy this recipe, cook in in an electric skillet and strain it and place it in the fridge for next time. I would do the same if I were to re-use the fat from the ground beef, strain and refrigerate.
My mother saved the bacon grease for other purposes, but she always got rid of the beef juice, because she felt it smoked to easily. I love cooking with tallow and bacon grease, and I don’t care if the flavor matches or not. It’s all good. 
As long as you keep the tallow/bacon nectar/lard in an airtight container, it doesn’t turn. I do. It’s fine. Easier to scoop out for the next use
And tallow is fine from non kidney fat too - if it’s ground beef juice, it may have other non fat liquid in it and may not be white as snow
Carl’s recent recipe for fried chicken recommended tallow and not lard, as the flavor with tallow was superior.
I’m no great fan of chicken and I’m only willing to try his recipe if I can use the fat which Carl believed gave the best flavor. If reusing fat from frying ground beef won’t do that, I’ll put off trying the recipe until I can obtain normal tallow.