Prelude of note in Italian romantic opera, originally (5)
I believe the answer is:
intro
'prelude' is the definition.
(I've seen this before)
'note in italian romantic opera originally' is the wordplay.
'note' becomes 'n' (abbreviation**).
'in' is an insertion indicator.
'italian' becomes 'it'.
'originally' suggests taking the first letters.
The initial letters of 'romantic opera' is 'ro'.
'n' put into 'it' is 'int'.
'int'+'ro'='INTRO'
'of' is the link.
(Other definitions for intro that I've seen before include "Opening passage (abbr)" , "Opening bars (abbr)" , "Beginning passage" , "First bars of a piece of popular music" , "Nitro (anag.)" .)