Fellow just revolting (9)
I believe the answer is:
frightful
'revolting' is the definition.
(thesaurus)
'fellow just' is the wordplay.
'fellow' becomes 'f' (abbreviation - of a society etc.).
'just' becomes 'rightful' ('rightful' can be similar in meaning to 'just').
'f'+'rightful'='FRIGHTFUL'
(Other definitions for frightful that I've seen before include "ugly" , "nasty" , "Terrible, awful" , "Appalling" , "ghastly" .)