Sort of light fitting that's seen on end of rifle? (7)
I believe the answer is:
bayonet
This clue is a double definition.
'sort of light fitting' is the first definition.
(type of light bulb)
'that's seen on end of rifle?' is the second definition.
(blade on the end of a rifle)
(Other definitions for bayonet that I've seen before include "Stabbing weapon" , "As soldier" , "Dagger fixed to rifle" , "Muzzle blade" , "Knife fixed to the end of a rifle" .)