Heard note from singer (5)
I believe the answer is:
tenor
'singer' is the definition.
(tenor is a kind of singer)
'heard note' is the wordplay.
'heard' shows a homophone (sound like).
'note' becomes 'tenner' (a ten pound sterling bank note).
'tenner' sounds like 'TENOR'.
'from' acts as a link.
(Other definitions for tenor that I've seen before include "Carreras, for example" , "Voice classification of Jose Carreras" , "One singing" , "range of 14 across [GIGLI]" , "Pavarotti, maybe" .)