Make improvements to (5)
I believe the answer is:
amend
'make improvements to' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for amend that I've seen before include "Modify, correct" , "Corrct error, make a minor aleration" , "Rectify" , "Make corrections to (eg, document)" , "Modify - edit" .)