Lawman infiltrates Capone operation to get intoxicant (7)
I believe the answer is:
alcopop
'intoxicant' is the definition.
(I know that alcopop is a type of intoxicant)
'lawman infiltrates capone operation' is the wordplay.
'lawman' becomes 'cop' (cop is a kind of lawman).
'infiltrates' means one lot of letters goes inside another.
'capone' becomes 'Al' (gangster Al Capone).
'operation' becomes 'op'.
'al'+'op'='alop'
'cop' put within 'alop' is 'ALCOPOP'.
'to get' is the link.
(Other definitions for alcopop that I've seen before include "Drink for young adults" , "fizzy drink" , "Intoxicating drink resembling a soft drink" , "Hard drink resembling a soft drink" , "Soft drink containing spirits" .)