Corrects the 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 in another clue).
'in' indicates putting letters inside.
'script' becomes 'ms' (I've seen this in other clues).
'a'+'ms'='ams'
'end' put within 'ams' is 'AMENDS'.
'the' acts as a link.
(Other definitions for amends that I've seen before include "Makes changes, to a text say" , "Make these to atone for wrong done" , "They're made to compensate" , "Make these to make up for past wrongs" , "It is made in reparation" .)