Mend; restore to good condition (6)
I believe the answer is:
repair
I believe this is a double definition.
'mend' is the first definition.
(I know that mend can be written as repair)
'restore to good condition' is the second definition.
(I've seen this before)
(Other definitions for repair that I've seen before include "Restore to working condition" , "Make good again" , "Patch up" , "Mend, restore to good condition" , "resort" .)