Sharp weapon (5)
'sharp weapon' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for sword that I've seen before include "Bladed weapon" , "Fencer's weapon" , "killer?" , "Sharp-edged weapon" , "Weapon with long blade" .)
(Other definitions for knife that I've seen before include "Edge tool" , "Eating utensil" , "Silent killer" , "Use this to carve" , "Cutting blade" .)