Artist again exceptional (4)
I believe the answer is:
rare
'exceptional' is the definition.
(I've seen this in another clue)
'artist again' is the wordplay.
'artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'again' becomes 're' (prefix meaning 'again').
'ra'+'re'='RARE'
(Other definitions for rare that I've seen before include "(Of meat) red" , "not dense" , "Rear up to be uncommon" , "Scarce as hen's teeth!" , "thin on the ground" .)