Nick farewell music (7)
I believe the answer is:
cantata
'music' is the definition.
(cantata is a kind of music)
'nick farewell' is the wordplay.
'nick' becomes 'can' (I am not sure about this - if you are sure you should believe this answer much more).
'farewell' becomes 'ta ta' (I've seen this in another clue).
'can'+'tata'='CANTATA'
Can you help me to learn more?
(Other definitions for cantata that I've seen before include "Work for accompanied voice" , "Sacred choral piece" , "Vocal-orchestral piece" , "Short oratorio performed in concert" , "Song" .)