From the movie Goodfellas:
Police to gangster: Talk to me. When was the last time you took a collar? Fuckhead, I'm talking to you.
I can't find anything on the Internet. Does "take a collar" mean "be questioned" or "be detained by police"?
"Collar" has a verbal meaning "to arrest or detain someone (MW) So this is related to "arrest" not "questioning" (This meaning dates back to the 1500s, from a meaning "grab someone by the neck")
A collar, then, in this context means "an act of being arrested". A little more context from the movie could make the exact meaning of "take a collar" clear. It seems to mean "allow oneself to be arrested for a crime committed by another person". Given that "Goodfellas" is about gangsters I suppose a low-level gangster might "take a collar" to protect a higher ranking gangster.