Bellini's sorry about rising composer (7)
I believe the answer is:
rossini
'composer' is the definition.
(I've seen this before)
'bellini's sorry about rising' is the wordplay.
'about' indicates a hidden word (the clue goes around or about the answer).
'rising' shows that the letters should be reversed in order (going up in a down clue).
'inissor' can be found hidden inside 'bellinis sorry'.
'inissor' back-to-front is 'ROSSINI'.
(Other definitions for rossini that I've seen before include "Italian composer, 1792-1868" , "Largo al factotum composer" , "Gioacchino ---, It. composer" , "Staff writer" , "opera producer" .)