Doctor with cry of approval, over-the-top, about opera (9)
I believe the answer is:
rigoletto
'opera' is the definition.
(I know that Rigoletto is a opera)
'doctor with cry of approval over-the-top about' is the wordplay.
'doctor' becomes 'rig' (I've seen this before).
'with' says to put letters next to each other.
'cry of approval' becomes 'ole' (Spanish exclamation of approval).
'over-the-top' becomes 'OTT' (abbreviation).
'about' is a reversal indicator.
'ott' reversed gives 'tto'.
'rig'+'ole'+'tto'='RIGOLETTO'
(Other definitions for rigoletto that I've seen before include "Verdi's hunchback jester" , "court favourite" , "titled man" , "Opera by Verdi" , "noted work" .)