They're subject to poaching (4)

I believe the answer is:

eggs

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'poaching' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.

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

Can you help me to learn more?

(Other definitions for eggs that I've seen before include "Incites - farm produce" , "Ova" , "Chickens lay them" , "Breakfast items" , "Roe" .)

I've seen this clue in the Evening Standard.

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