Piece of music from show, Oscar's first (8)
I believe the answer is:
concerto
'piece of music' is the definition.
(concerto is a type of musical composition)
'show oscar's first' is the wordplay.
'show' becomes 'concert' (concert is a kind of show).
'oscar's first' becomes 'o' (cst letter of 'oscar').
'concert'+'o'='CONCERTO'
'from' acts as a link.
(Other definitions for concerto that I've seen before include "10 [COMPOSITION]" , "Work for soloist and orchestra" , "Composition for accompanied soloist" , "Musical composition" , "Work for orchestra and soloist(s)" .)