Present mafioso polished off (6)
I believe the answer is:
donate
'present' is the definition.
(donating is a kind of presenting)
'mafioso polished off' is the wordplay.
'mafioso' becomes 'Don'.
'polished off' becomes 'ate' (I've seen this in other clues).
'don'+'ate'='DONATE'
(Other definitions for donate that I've seen before include "give in kindness" , "Contribute (to charity)" , "Contribute charitably" , "Give as a gift as to charity" , "Give money to charity" .)