Own up to (5)
'own up to' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for admit that I've seen before include "receive" , "Reveal" , "Confess; allow in" , "Allow to enter; own up" , "Disclose" .)
(Other definitions for cop that I've seen before include "Member of the police force and an arrest" , "catch" , "Short policeman" , "Police officer (slang)" , "Policeman (slang)" .)