Bad art's seldom produced by great painters (3,7)
I believe the answer is:
old masters
'great painters' is the definition.
'old masters' can be an answer for 'painters' (old master is a kind of painter). I am not sure about the 'great' bit.
'bad art's seldom produced by' is the wordplay.
'bad' indicates anagramming the letters.
'produced by' means one lot of letters go next to another.
'arts' after 'seldom' is 'seldomarts'.
'seldomarts' with letters rearranged gives 'OLD MASTERS'.
Can you help me to learn more?
(Other definitions for old masters that I've seen before include "Great Renaissance paintings" , "Classic artists" , "Great historic artists" , "Great works" , "Art's models (anag) - classic painters" .)