Bears used as weapon (5)
I believe the answer is:
sabre
'weapon' is the definition.
(sabre is a kind of weapon)
'bears used' is the wordplay.
'used' is an anagram indicator.
'bears' with letters rearranged gives '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" .)