Two items on the afternoon menu for one?

I believe the answer is:

teacake

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

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for teacake that I've seen before include "food item" , "Sweet bun" , "Bun for toasting" , "Scones with raisins, toasted and buttered" , "Fruited bun" .)

I've seen this clue in The Telegraph.

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