More old paintings returned (5)
I believe the answer is:
extra
'more' is the definition.
(thesaurus)
'old paintings returned' is the wordplay.
'old' becomes 'ex'.
'paintings' becomes 'art' (I've seen this before).
'returned' says the letters should be written in reverse.
'art' in reverse letter order is 'tra'.
'ex'+'tra'='EXTRA'
(Other definitions for extra that I've seen before include "There's more" , "particularly" , "Left over" , "eg Wide; additional" , "Small part actor" .)