An old-fashioned gangster’s gun? (3)
I believe the answer is:
gat
'gangster's gun?' is the definition.
(I've seen this before)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for gat that I've seen before include "Gangster's gun" , "Piece" , "in Indian music, the last bit of raga" , "weapon" , "Slang for a gangster's pistol" .)