Correct your setter in conclusion (5)
I believe the answer is:
emend
'correct' is the definition.
(I've seen this in another clue)
'your setter in conclusion' is the wordplay.
'your setter' becomes 'me' (the crossword setter of this puzzle).
'in' indicates putting letters inside.
'conclusion' becomes 'end' (something's conclusion is its end).
'me' put inside 'end' is 'EMEND'.
(Other definitions for emend that I've seen before include "Improve by editing" , "Improve (texts)" , "Remove faults from" , "make an improvement" , "Make improvements to (text)" .)