"En garde” weapon (4)
I believe the answer is:
epee
'en garde weapon' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for epee that I've seen before include "Fencing blade" , "Narrow fencing sword" , "Fencing sword similar to a foil" , "Fighting blade" , "Another fencing sword" .)