Bears dreadful weapon (5)
I believe the answer is:
sabre
'weapon' is the definition.
(I know this)
'bears dreadful' is the wordplay.
'dreadful' indicates anagramming the letters.
'bears' is an anagram of 'SABRE'.
(Other definitions for sabre that I've seen before include "weapon" , "Walt --, cartoonist" , "Sword with curved blade" , "Large wasp" , "Type of sword" .)