Leave variable note for an artist (4)
I believe the answer is:
goya
'for an artist' is the definition.
(Francisco Goya)
'leave variable note' is the wordplay.
'leave' becomes 'go' (to go is to depart or leave).
'variable' becomes 'y' (algebra).
'note' becomes 'a' (musical note).
'go'+'y'+'a'='GOYA'
(Other definitions for goya that I've seen before include "Great Spanish painter who depicted horrors of war" , "Spanish painter, d. 1828" , "Span. C18 court painter" , "Francesco de ---, Sp. court painter" , "Portrait painter" .)