Masked gangster shot Spanish gentleman (7)
I believe the answer is:
hidalgo
'spanish gentleman' is the definition.
(I've seen this before)
'masked gangster shot' is the wordplay.
'masked' becomes 'hid' (I've seen this in another clue).
'gangster' becomes 'al' (Al Capone).
'shot' becomes 'go' (both can mean an attempt).
'hid'+'al'+'go'='HIDALGO'
(Other definitions for hidalgo that I've seen before include "foreign gentleman" , "Spanish nobleman" , "Pachuca is capital of this Mexican state" , "Grandee" , "Spanish aristocrat" .)