Mend broken rapier (6)
I believe the answer is:
repair
'mend' is the definition.
(I know that mend can be written as repair)
'broken rapier' is the wordplay.
'broken' indicates an anagram.
'rapier' anagrammed gives 'REPAIR'.
(Other definitions for repair that I've seen before include "Mend, restore to good condition" , "Restore (something) to good condition" , "remedy" , "Withdraw" , "Patch up" .)