Notes, we hear, for singers (6)
I believe the answer is:
tenors
'singers' is the definition.
(tenor is a singing voice)
'notes we hear' is the wordplay.
'notes' becomes 'tenners' (ten pound notes).
'we hear' indicates a 'sounds like' (homophone) clue.
'tenners' sounds like 'TENORS'.
'for' is the link.
(Other definitions for tenors that I've seen before include "Male singers from Reston" , "Male singers with high register" , "Opera singers" , "Male singing voices" .)