Hat one for Scarface? (6)
I believe the answer is:
capone
'for scarface?' is the definition.
(I've seen this in another clue)
'hat one' is the wordplay.
'hat' becomes 'cap' (I've seen this before).
'cap'+'one'='CAPONE'
(Other definitions for capone that I've seen before include "Chicago gangster, d. 1947" , "Mountain said to be resting place of Noah's Ark" , "Al ..., US gangster" , "Notorious criminal" , "US gangster (St Valentine's Day massacre)" .)