Improve and take me back before the finish (5)
I believe the answer is:
emend
'improve' is the definition.
(emending is a kind of improving)
'me back before the finish' is the wordplay.
'back' says the letters should be written in reverse.
'before' is a charade indicator (letters next to each other).
'the finish' becomes 'end' (I've seen this in other clues).
'me' written backwards gives 'em'.
'em'+'end'='EMEND'
'and take' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for emend that I've seen before include "Correct/revise (a text)" , "make an improvement" , "Revise (a text) (E, not A)" , "would appear better" , "Improve by altering" .)