Society rebuffed my fake orchestral piece (8)
I believe the answer is:
symphony
'orchestral piece' is the definition.
(I've seen this in another clue)
'society rebuffed my fake' is the wordplay.
'society' becomes 's' (common abbreviation in names of organisations).
'rebuffed' shows that the letters should be reversed in order.
'fake' becomes 'phony' (synonyms).
'my' in reverse letter order is 'ym'.
's'+'ym'+'phony'='SYMPHONY'
(Other definitions for symphony that I've seen before include "piece of music" , "Musical composition" , "Eg, the Eroica" , "Composition for an orchestra" , "Large orchestral piece" .)