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