Arrest a guy with a companion (5)
I believe the answer is:
catch
'arrest' is the definition.
(synonyms)
'a guy with a companion' is the wordplay.
'a guy' becomes 'cat' (American slang for man, esp in Jazz).
'with' is a charade indicator (letters next to each other).
'a companion' becomes 'ch' (Companion of Honour).
'cat'+'ch'='CATCH'
(Other definitions for catch that I've seen before include "Trap - hear - contract" , "Grab hold of - fastener" , "Grab; disadvantage" , "It's taken by a fielder to dismiss a player in baseball and cricket" , "potential partner?" .)