Artist imprisoned by a bitter twisted judge (9)
I believe the answer is:
arbitrate
'judge' is the definition.
(thesaurus)
'artist imprisoned by a bitter twisted' is the wordplay.
'artist' becomes 'ra' (Royal Academician, member of Royal Academy of Arts).
'imprisoned by' indicates putting letters inside.
'twisted' is an anagram indicator.
'a'+'bitter'='abitter'
'abitter' anagrammed gives 'arbitte'.
'ra' placed within 'arbitte' is 'ARBITRATE'.
(Other definitions for arbitrate that I've seen before include "Adjudge" , "Act between disputing parties" , "Mediate" , "judge" , "Decide" .)