Terminated gangster’s romantic partner (3,4)
I believe the answer is:
all over
'terminated' is the definition.
(synonyms)
'gangster's romantic partner' is the wordplay.
'gangster' becomes 'al' (Al Capone).
'romantic partner' becomes 'lover' (I've seen this before).
'al'+'lover'='ALL-OVER'
(Other definitions for all over that I've seen before include "typically" , "Excessively attentive" , "very characteristically" , "covering everything" , "Finished" .)