Heard singer rendering note (6)
I believe the answer is:
tenner
'note' is the definition.
(a ten pound sterling bank note)
'heard singer' is the wordplay.
'heard' indicates a 'sounds like' (homophone) clue.
'singer' becomes 'tenor' (tenor is a kind of singer).
'tenor' is a homophone of 'TENNER'.
'rendering' is the link.
(Other definitions for tenner that I've seen before include "British banknote" , "note form" , "British note" , "PS10" , "A spot of money" .)