Progressive artist caught in ring (7)
I believe the answer is:
radical
'progressive' is the definition.
(thesaurus)
'artist caught in ring' is the wordplay.
'artist' becomes 'ra' (Royal Academician, member of Royal Academy of Arts).
'caught' becomes 'c' (cricket abbreviation).
'in' indicates putting letters inside.
'ring' becomes 'dial' (I've seen this before).
'c' inserted into 'dial' is 'dical'.
'ra'+'dical'='RADICAL'
(Other definitions for radical that I've seen before include "Deep" , "Drastic or thorough as changes may be" , "Complete" , "Person with extreme political views" , "Thoroughgoing - (popularly) extremist" .)