Composer spoken of as 'performance god' (6)
I believe the answer is:
chopin
'composer' is the definition.
(Frederic Chopin)
'spoken of as performance god' is the wordplay.
I cannot quite see how this works, but
'of' could be 'o' and 'o' is found in the answer.
'as' could be 'in' (I've seen this in other clues) and 'in' is found in the answer.
This explanation may well be incorrect...
(Other definitions for chopin that I've seen before include "Double centenarian" , "No chip on this composer's shoulder" , "Composer of mainly piano works" , "Polish composer and pianist, d. 1849" , "Frederic . . . . . ., great 19th century Polish composer" .)