Gentleman returned extravagant starter of opulent rice dish (7)
I believe the answer is:
risotto
'rice dish' is the definition.
(I've seen this before)
'gentleman returned extravagant starter of opulent' is the wordplay.
'gentleman' becomes 'sir' (I've seen this before).
'returned' says the letters should be written in reverse.
'extravagant' becomes 'ott' (I've seen this in other clues).
'starter of' indicates taking the first letters.
The first letter of 'opulent' is 'o'.
'sir' back-to-front is 'ris'.
'ris'+'ott'+'o'='RISOTTO'
(Other definitions for risotto that I've seen before include "Savoury rice dish" , "Perhaps Italian" , "Italian dish of rice, meat and vegetables" , "scoff" , "Italian recipe" .)