Abundant defamation written about artist (7)
I believe the answer is:
liberal
'abundant' is the definition.
(thesaurus)
'defamation written about artist' is the wordplay.
'defamation' becomes 'libel' (libel is a kind of defamation).
'written about' indicates putting letters inside.
'artist' becomes 'ra' (Royal Academician, member of Royal Academy of Arts).
'libel' enclosing 'ra' is 'LIBERAL'.
(Other definitions for liberal that I've seen before include "Lavish" , "Bountiful" , "Ample; former politician" , "In favour of policies of progress and reform" , "open to new ideas" .)