Starts off aria like true opera singer (4)
I believe the answer is:
alto
'singer' is the definition.
(alto is a kind of singer)
'starts off aria like true opera' is the wordplay.
'starts off' suggests taking the first letters.
The initial letters of 'aria like true opera' is 'ALTO'.
(Other definitions for alto that I've seen before include "Member of choir" , "A singing voice or pitch" , "The highest adult male singing-voice" , "One who sings" , "Male singer" .)