"Is there some fat on the meat?"
Translation:Ĉu estas iom da graso sur la viando?
I suspect that it could be either “in” or “on” depending on the meat. With some meats you have streaks of fat running through the meat (such as streaky bacon) where “in” would be more appropriate. Some meats have a more significant layer of fat on the outside where “on” would be better, but “around” might be better still.
Is there a reason we need "da" in this sentence? I read this as: Is there some of fat on the meat.
Iom means "Some amount" not just "some." So what the sentence says is "some quantity of fat…" Which is why da is here.