A shot gun (6)
I believe the answer is:
cannon
This clue is a double definition.
'a shot' is the first definition.
(cannon is a kind of shot)
'gun' is the second definition.
(cannon is a kind of gun)
(Other definitions for cannon that I've seen before include "Howitzer" , "Great gun" , "mortar" , "Billiard shot or large gun" , "Billiard shot in which player's ball hits the two others" .)