Breakfast show in instalments, reportedly (6)
I believe the answer is:
cereal
'breakfast' is the definition.
(I've seen this before)
'in instalments reportedly' is the wordplay.
'in instalments' becomes 'serial' (I've seen this before).
'reportedly' shows a homophone (sound like).
'serial' is a homophone of 'CEREAL'.
'show' is the link.
(Other definitions for cereal that I've seen before include "Common part of breakfast" , "Eg, wheat, rice" , "Grass cultivated for food" , "Breakfast dish" , "Food prepared from grain" .)