Note produced by opera singer on radio (6)
I believe the answer is:
tenner
'note produced by opera' is the definition.
'tenner' can be an answer for 'note' (a ten pound sterling bank note). I'm not sure about the 'produced by opera' bit.
'singer on radio' is the wordplay.
'singer' becomes 'tenor' (tenor is a kind of singer).
'on radio' shows a homophone (sound like).
'tenor' is a homophone of 'TENNER'.
Can you help me to learn more?
(Other definitions for tenner that I've seen before include "Cash note" , "British banknote" , "Banknote (informal); sounds like a singer" , "A spot of money" , "A 10 pound note (colloq.)" .)