“Plenty of booze,” the policeman put in (5)
I believe the answer is:
ample
'plenty' is the definition.
(thesaurus)
'booze the policeman put in' is the wordplay.
'booze' becomes 'ale' (I've seen this before).
'the policeman' becomes 'mp' (abbreviation for Military Policeman).
'put in' is an insertion indicator.
'ale' enclosing 'mp' is 'AMPLE'.
'of' acts as a link.
(Other definitions for ample that I've seen before include "Full-figured" , "Big" , "Generous" , "Plentiful; capacious" , "Fairly large" .)