What’s this in Warhol being a great artist? (7)
I believe the answer is:
holbein
'artist?' is the definition.
(Hans Holbein the Younger or Hans Holbein the Elder)
'what's this in warhol being a great' is the wordplay.
'what's this in' says the answer is hidden in the clue.
'HOLBEIN' is hidden in the letters of 'warhol being great'.
(Other definitions for holbein that I've seen before include "Hans -, court painter to Henry VIII" , "Hans ---, painted Erasmus, More" , "Hans --, one of two related German painters" , "Hans -, German artist who painted Henry VIII" , "Hans -, German painter (father or son)" .)