Pirate gets a bit of a shock, finding gun (9)
I believe the answer is:
flintlock
'gun' is the definition.
(I know that flintlock is a type of Handgun)
'pirate gets a bit of a shock' is the wordplay.
'pirate' becomes 'flint' (Captain Flint from Treasure Island).
'gets' means one lot of letters go next to another.
'a bit of a shock' becomes 'lock' (shock can mean a mass of hair).
'flint'+'lock'='FLINTLOCK'
'finding' acts as a link.
(Other definitions for flintlock that I've seen before include "gun" , "Old-fashioned firearm" , "arm" , "Old musket" , "one was fired" .)