Old unfinished Degas rejected (4)
I believe the answer is:
aged
'old' is the definition.
(similar in meaning)
'unfinished degas rejected' is the wordplay.
'unfinished' means to remove the last letter.
'rejected' says the letters should be written backwards.
'degas' with its last letter taken off is 'dega'.
'dega' reversed gives 'AGED'.
(Other definitions for aged that I've seen before include "Ripened, matured" , "Antiquated" , "Old or ancient" , "Very old, person or wine" , "Senescent" .)