Magnificent concert piano (5)
I believe the answer is:
grand
I believe this clue is a double definition.
'magnificent' is the first definition.
(I've seen this in another clue)
'concert piano' is the second definition.
(I've seen this in another clue)
(Other definitions for grand that I've seen before include "1000, colloquially" , "Magnificent, imposing" , "Stately - splendid" , "great distinction" , "Impressive, large" .)