Corrects final part in a script (6)
I believe the answer is:
amends
'corrects' is the definition.
(amending is a kind of correcting)
'final part in a script' is the wordplay.
'final part' becomes 'end' (I've seen this before).
'in' means one lot of letters goes inside another.
'script' becomes 'ms' (I've seen this in other clues).
'a'+'ms'='ams'
'end' put inside 'ams' is 'AMENDS'.
(Other definitions for amends that I've seen before include "Make these to right wrong" , "Compensation" , "Make these to atone for injuries or loss caused" , "Alters and improves" , "Changes for the better" .)