Give way over cereal (4)
I believe the answer is:
sago
'cereal' is the definition.
(edible starch)
'give way over' is the wordplay.
'give way' becomes 'sag' (to sag is to give way or collapse).
'over' becomes 'o' (cricket abbreviation).
'sag'+'o'='SAGO'
(Other definitions for sago that I've seen before include "Starchy pudding cereal" , "Starchy cereal used in puddings" , "Edible powdery starch" , "Powdery starch from a palm" , "Edible palm starch" .)