Work on piano unveiling symphony initially (4)
I believe the answer is:
opus
'work' is the definition.
(I've seen this before)
'on piano unveiling symphony initially' is the wordplay.
'initially' indicates taking the first letters.
The initial letters of 'on piano unveiling symphony' is 'OPUS'.
(Other definitions for opus that I've seen before include "Piece of music (with number)" , "Composer's work" , "Composition - magnum __" , "A Latin work" , "Work of 25 perhaps" .)