Work of art seldom produced (3,6)
I believe the answer is:
Here is my best explanation:
'work' is the definition.
'art seldom produced' is the subsidiary indication.
'produced' is an anagram indicator.
'artseldom' with letters rearranged gives 'oldmaster'.
'of' is the link.
(Other definitions for old master that I've seen before include "Michelangelo perhaps", "Mr Chips, say?", "Great painting of former times", "Classic painter", "Could get a picture", "soon to retire from school?", "Great painter of former times - or one of his works", "special picture", "Famous painting" and "Classic painting".)