Old king painting Ben (6)
I believe the answer is:
arthur
'old king' is the definition.
(I've seen this before)
'painting ben' is the wordplay.
'painting' becomes 'art' (painting is an art).
'ben' becomes 'hur' (ben hur is a religious drama film).
'art'+'hur'='ARTHUR'
(Other definitions for arthur that I've seen before include "Dudley Moore film" , "Legendary king of the Britons" , "Excalibur king" , "Owner of Excalibur" , "Legendary king of Camelot." .)