A Rice Krispies mascot (4)
I believe the answer is:
snap
'a rice krispies mascot' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for snap that I've seen before include "Break; liveliness" , "Pans out in simple card game" , "give way" , "piece of cake" , "Break suddenly with cracking sound" .)