Counter sword (4)
I believe the answer is:
foil
I believe this clue is a double definition.
'counter' is the first definition.
(thesaurus)
'sword' is the second definition.
(foil is a kind of sword)
(Other definitions for foil that I've seen before include "Parry" , "thin plate of metal" , "Tharwt with Sword" , "Frustrate; kitchen wrap" , "Repulse" .)