Former partner has taken up painting more (5)
I believe the answer is:
extra
'more' is the definition.
(thesaurus)
'former partner has taken up painting' is the wordplay.
'former partner' becomes 'ex'.
'has' is a charade indicator (letters next to each other).
'taken up' is a reversal indicator.
'painting' becomes 'art' (I've seen this before).
'art' back-to-front is 'tra'.
'ex'+'tra'='EXTRA'
(Other definitions for extra that I've seen before include "Bit actor in film" , "Bit actor in crowd scene" , "Bye or wide, for example" , "Not a standard item" , "Bit actor in movie's crowd scenes" .)