Bears used as weapon (5)
I believe the answer is:
sabre
'weapon' is the definition.
(I know that sabre is a type of sword)
'bears used' is the wordplay.
'used' indicates an anagram.
'bears' is an anagram of 'SABRE'.
'as' acts as a link.
(Other definitions for sabre that I've seen before include "Heavy cavalry sword" , "Sword with curved blade" , "Large wasp" , "Bares (anag.)" , "Slasher" .)