Starchy food as starter will do, we're told (4)
I believe the answer is:
sago
'starchy food' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for sago that I've seen before include "Starchy cereal used in puddings" , "Starchy pudding cereal" , "Starchy grain used in desserts" , "dessert?" , "Cereal, used in pudding" .)