Catch a police officer (3)
I believe the answer is:
cop
I believe this is a triple definition!
'catch' is the first definition.
(cop can mean to arrest or apprehend)
'a police' is the second definition.
(thesaurus)
'officer' is the third definition.
(cop is a kind of officer)
(Other definitions for cop that I've seen before include "busy" , "Short policeman" , "catch" , "Policeman (informal)" , "An American policeman" .)