Broad-minded artist involved in slander (7)
I believe the answer is:
liberal
'broad-minded' is the definition.
(similar in meaning)
'artist involved in slander' is the wordplay.
'artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'involved in' is an insertion indicator.
'slander' becomes 'libel' (libeling is a kind of slandering).
'ra' going within 'libel' is 'LIBERAL'.
(Other definitions for liberal that I've seen before include "Large-minded" , "Ample; former politician" , "Bountiful" , "Broad-minded in Braille" , "Braille (anag.)" .)