Soap opera on the radio for breakfast (6)
I believe the answer is:
cereal
'for breakfast' is the definition.
(I've seen this before)
'soap opera on the radio' is the wordplay.
'soap opera' becomes 'serial' (I've seen this in another clue).
'on the radio' indicates a 'sounds like' (homophone) clue.
'serial' is a homophone of 'CEREAL'.
(Other definitions for cereal that I've seen before include "Grain crop" , "Something for brekkie" , "Food prepared from grain" , "Eg, wheat, rice" , "Eg, wheat, rye, corn" .)