Staple item on the early bird menu? (4)

I believe the answer is:

worm

'item on the early bird menu?' is the definition.
(the early bird catches the worm)

I don't understand how the remainder of the clue works.

(Other definitions for worm that I've seen before include "Cylindrical gear; burrowing invertebrate" , "Reproductive computer virus" , "Screw thread; maggot" , "mean creature" , "Insect larva" .)

I've seen this clue in The Guardian.

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