Poem, unfinished, in real turnabout (8)
I believe the answer is:
reversal
'turnabout' is the definition.
(I know that turnabout can be written as reversal)
'poem unfinished in real' is the wordplay.
'poem' becomes 'verse' (verse is a kind of poem).
'unfinished' means to remove the last letter.
'in' means one lot of letters goes inside another.
'verse' with its final letter removed is 'vers'.
'vers' inserted within 'real' is 'REVERSAL'.
(Other definitions for reversal that I've seen before include "Set back" , "About-turn" , "that makes no difference to mum or dad" , "change of heart" , "Turnaround - defeat" .)