Fuss made by supporter attending do (7)
I believe the answer is:
fanfare
'fuss' is the definition.
(thesaurus)
'supporter attending do' is the wordplay.
'supporter' becomes 'fan' (fan is a kind of supporter).
'attending' says to put letters next to each other.
'do' becomes 'fare' ('fare' can be a synonym of 'do'**).
'fan'+'fare'='FANFARE'
'made by' acts as a link.
(Other definitions for fanfare that I've seen before include "Brass flourish" , "Musical flourish" , "Naff era (anag)" , "elaborate ceremony" , "Ceremonious sounding of trumpets" .)