Finish off final performance for old actress (7)
I believe the answer is:
swanson
'old actress' is the definition.
(I've seen this before)
'finish off final performance' is the wordplay.
'finish off' means to remove the last letter.
'final performance' becomes 'swansong' (I've seen this before).
'swansong' with its final letter taken off is 'SWANSON'.
'for' acts as a link.
(Other definitions for swanson that I've seen before include "Gloria, silent film star" , "Old actress" , "She acted" , "old film star" , "Screen star" .)