Decadent oriental fellow to celebrate (6)
I believe the answer is:
effete
'decadent' is the definition.
('effete' can be a synonym of 'decadent')
'oriental fellow to celebrate' is the wordplay.
'oriental' becomes 'e'.
'fellow' becomes 'f' (abbreviation - of a society etc.).
'to celebrate' becomes 'fete' ('fete' can be a synonym of 'celebrate').
'e'+'f'+'fete'='EFFETE'
(Other definitions for effete that I've seen before include "Over-refined and ineffectual" , "Enfeebled" , "Spent; degenerate" , "Over-refined, exhausted" , "Weak, decadent" .)