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