Charles perhaps against appearing in demo (7)
I believe the answer is:
monarch
'charles' is the definition.
(King Charles)
'against appearing in demo' is the wordplay.
'against' becomes 'on' (on can mean by or up against).
'appearing in' indicates putting letters inside.
'demo' becomes 'march' (demonstration).
'on' placed within 'march' is 'MONARCH'.
'perhaps' is the link.
(Other definitions for monarch that I've seen before include "Not a subject" , "Sovereign; butterfly" , "Butterfly - ruler" , "Butterfly (emperor, say?)" , "one over realm?" .)