Old French artist not quite up (4)
I believe the answer is:
aged
'old' is the definition.
(similar in meaning)
'french artist not quite up' is the wordplay.
'french artist' becomes 'degas' (Edgar Degas, 1834-1917).
'not quite' means to remove the last letter (most but not all of the word).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'degas' with its final letter taken away is 'dega'.
'dega' written backwards gives 'AGED'.
(Other definitions for aged that I've seen before include "not a modern copy" , "Antiquated" , "way over the hill" , "well over the hill" , "Ripened, matured" .)