Anti-regalia, possibly, being against class distinction (11)
I believe the answer is:
egalitarian
'against class distinction' is the definition.
(against the class system)
'anti-regalia possibly' is the wordplay.
'possibly' indicates an anagram.
'anti'+'regalia'='antiregalia'
'antiregalia' is an anagram of 'EGALITARIAN'.
'being' is the link.
(Other definitions for egalitarian that I've seen before include "One favouring equality" , "Based on the principle all are equal" , "Equity advocate" , "Believing in equality" , "In favour of equality" .)