On radio not many would quarrel (4)
I believe the answer is:
feud
'quarrel' is the definition.
(I've seen this before)
'on radio not many would' is the wordplay.
I cannot quite understand how this works, but
'many' could be 'd' (Roman numeral for 500) and 'd' is present in the answer.
The remaining letters 'feu' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for feud that I've seen before include "Quarrel; spat" , "Persistent strife" , "Squabble" , "Bitter disagreement between families" , "State of prolonged mutual hostility" .)