Blade on a rifle (7)
I believe the answer is:
bayonet
'blade on a rifle' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for bayonet that I've seen before include "one's attached to one's rifle - that's sort of fitting" , "Pointed weapon" , "Knife fixed to the end of a rifle" , "Neat boy (anag.)" , "Muzzle blade" .)