Axe policeman for smuggling heroin (7)
I believe the answer is:
chopper
'axe' is the definition.
(I've seen this before)
'policeman for smuggling heroin' is the wordplay.
'policeman' becomes 'copper' (copper can informally mean a police officer).
'for smuggling' is an insertion indicator (some letters smuggled inside).
'heroin' becomes 'H' (H is a slang term for heroin).
'copper' enclosing 'h' is 'CHOPPER'.
(Other definitions for chopper that I've seen before include "An informal helicopter, or an axe" , "Butcher's cleaver" , "An axe, or a slang helicopter" , "Helicopter (sl.)" , "that comes down on the block?" .)