About to express regret about piano, one Italian composer (8)
I believe the answer is:
respighi
'composer' is the definition.
(I know that Respighi is a composer)
'about to express regret about piano one italian' is the wordplay.
'about' becomes 're' ('re' means regarding or about).
'to express regret' becomes 'sigh' (a sigh expresses regret).
'about' is an insertion indicator.
'piano one' becomes 'p' (rst letter of 'pi').
'italian' becomes 'I' (abbreviation for Italian).
'sigh' going around 'p' is 'spigh'.
're'+'spigh'+'i'='RESPIGHI'
(Other definitions for respighi that I've seen before include "Italian composer of symphonic poems, d. 1936 - hire pigs (anag)" , "Irish peg, oddly, for the Italian composer" , "Italian composer (The Pines of Rome)" , "he scored!" , "Italian barman" .)