Upper class leading artist (3,6)
I believe the answer is:
top drawer
'upper class' is the definition.
(I've seen this before)
'leading artist' is the wordplay.
'leading' becomes 'top' (both can mean first-class).
'artist' becomes 'drawer' (drawer is a kind of artist).
'top'+'drawer'='TOP-DRAWER'
(Other definitions for top drawer that I've seen before include "highest quality" , "main attraction" , "Upper-class" , "Highest level of society" , "People of the highest standing" .)