Fancy better cereal (7)
I believe the answer is:
caprice
'fancy' is the definition.
(thesaurus)
'better cereal' is the wordplay.
'better' becomes 'cap' (I've seen this before).
'cereal' becomes 'rice' (rice is a kind of cereal).
'cap'+'rice'='CAPRICE'
(Other definitions for caprice that I've seen before include "A whim or piece of fancy" , "Sudden change of mind" , "Sudden mood change" , "Whimsy" , "'Impulse, whim (7)'" .)