I hear, say when to start with the starch! (4)

I believe the answer is:

sago

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'the starch' is the definition.
(sago is a kind of starch)

I don't understand the remainder of the clue.

(Other definitions for sago that I've seen before include "Type of milk pudding" , "Starchy food as white pudding" , "Edible powdery starch" , "Edible palm starch" , "Starchy pudding cereal" .)

I've seen this clue in the Sydney Morning Herald.

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