Brought up breakfast cereal, bypassing the beginning of stomach and small intestine (5)

I believe the answer is:

ileum

'small intestine' is the definition.
(ileum is a kind of small intestine)

I can't explain the rest of the clue.

(Other definitions for ileum that I've seen before include "Part of intestines" , "Part of digestive system" , "part of the gut" , "Food processor" , "Part of canal" .)

I've seen this clue in The Guardian.

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