Gold disc follows rendition of Rita Ora's debut musical composition (8)
I believe the answer is:
oratorio
'musical composition' is the definition.
(type of musical composition)
'gold disc follows rendition of rita ora's debut' is the wordplay.
'gold' becomes 'or' ('or' is the heraldic name for gold).
'disc' becomes 'O' (disc-shaped letter).
'follows' says to put letters next to each other.
'rendition of' is an anagram indicator (I've seen 'rendition' mean this).
'debut' indicates taking the first letters.
The initial letter of 'oras' is 'o'.
'rita'+'o'='ritao'
'ritao' is an anagram of 'atori'.
'o' after 'atori' is 'atorio'.
'or'+'atorio'='ORATORIO'
(Other definitions for oratorio that I've seen before include "Eg, The Seasons (Haydn)" , "I, too, roar at sacred music" , "Handel's Messiah, for example" , "Music for many performers" , "Work for voices, chorus and orchestra with biblical theme" .)