After returning before noon, Sir Walter doesn't finish 'The Talisman (6)
I believe the answer is:
mascot
''the talisman' is the definition.
('mascot' can be a synonym of 'talisman')
'after returning before noon sir walter doesn't finish' is the wordplay.
'after returning' says the letters should be written backwards.
'before noon' becomes 'am' (as in AM on a clock).
'sir walter' becomes 'scott' (I've seen this in another clue).
'doesn't finish' means to remove the last letter.
'am' back-to-front is 'ma'.
'scott' with its final letter taken off is 'scot'.
'ma'+'scot'='MASCOT'
(Other definitions for mascot that I've seen before include "Symbolic lucky figure" , "Thing considered to bring good luck" , "Bringer of good luck to team, etc" , "Charm - talisman" , "Lucky talisman" .)