Change myself, to take part in the finale (5)
I believe the answer is:
emend
'change' is the definition.
(I've seen this before)
'myself to take part in the finale' is the wordplay.
'myself' becomes 'me'.
'to take part in' is an insertion indicator.
'the finale' becomes 'end' (I've seen this in another clue).
'me' placed into 'end' is 'EMEND'.
(Other definitions for emend that I've seen before include "Make correction in written material" , "Correct/revise (a text)" , "make an improvement" , "Correct, revise (text)" , "Improve (writing)" .)