Clip-fed submachine gun (4)
I believe the answer is:
bren
'clip-fed submachine gun' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for bren that I've seen before include "Weapon" , "Machine-gun" , "World War Two machine gun" , "Light machine gun (made in Brno and Enfield)" .)