Rembrandt or Rubens (3,6)
I believe the answer is:
old master
'rembrandt or rubens' is the definition.
(I know that Rembrandt is a old master)
This is the entire clue.
(Other definitions for old master that I've seen before include "Do armlets serve for great painter of yore?" , "Classic painting" , "great artist" , "Liege lord" , "Michelangelo perhaps" .)