A lot of money for a piece of music (7)
I believe the answer is:
fortune
'a lot of money' is the definition.
(I've seen this before)
'for a piece of music' is the wordplay.
'a piece of music' becomes 'tune' (I've seen this in another clue).
'for'+'tune'='FORTUNE'
(Other definitions for fortune that I've seen before include "large sum of money" , "Fate, destiny" , "Huge amount of money" , "Providence" , "A lot of money - luck" .)