Write a splendid piece for the piano (3)
I believe the answer is:
pen
'write' is the definition.
(I know that write can be written as pen)
'a splendid piece for the piano' is the wordplay.
'a splendid piece' becomes 'en' (I am not sure about this - if you are sure you should believe this answer much more).
'for' says to put letters next to each other (I've seen this in other clues).
'the piano' becomes 'p' (musical abbreviation).
'en' after 'p' is 'PEN'.
Can you help me to learn more?
(Other definitions for pen that I've seen before include "International Association of poets, playwrights etc" , "dash off" , "Swan for the writer" , "American jug?" , "Writing implement" .)