One of the Rice Krispies mascots (4)
I believe the answer is:
snap
'one of the rice krispies mascots' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for snap that I've seen before include "Crack - shot" , "Lose cool" , "Break with a crack" , "Informal photograph" , "Break off - card-game" .)