More old paintings rejected (5)
I believe the answer is:
extra
'more' is the definition.
(I've seen this in other clues)
'old paintings rejected' is the wordplay.
'old' becomes 'ex' (prefix meaning former or onetime).
'paintings' becomes 'art' (painting is a type of artwork).
'rejected' shows that the letters should be reversed in order.
'art' reversed gives 'tra'.
'ex'+'tra'='EXTRA'
(Other definitions for extra that I've seen before include "like one of the crowd" , "Surplus to requirements" , "Accessory" , "not included" , "non-standard item" .)