Repair broken sword (6)
I believe the answer is:
rapier
'sword' is the definition.
(sword used in fencing)
'repair broken' is the wordplay.
'broken' is an anagram indicator.
'repair' with letters rearranged gives 'RAPIER'.
(Other definitions for rapier that I've seen before include "A thin double-edged sword" , "A fencing sword for repair" , "Light sword" , "Straight narrow sword with two edges" , "Sword for thrusting" .)