Police officer is man convulsed with greed (8)
I believe the answer is:
gendarme
'police officer' is the definition.
(gendarme is a kind of police officer)
'man convulsed with greed' is the wordplay.
'convulsed with' is an anagram indicator (letters convulse or shake).
'man' with its letters mixed up with 'greed' can make 'GENDARME'.
'is' acts as a link.
(Other definitions for gendarme that I've seen before include "Law enforcer" , "Force man" , "French Connection cop" , "Busy" , "see in Paris!" .)