A number whizz about, spinning after regular servings of tequila (5)

I believe the answer is:

euler

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'tequila' is the definition.
Both the answer and definition are singular nouns.
Maybe there's a link between them I don't understand?

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

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(Other definitions for euler that I've seen before include "Leonhard -, C-eighteen Swiss mathematician" , "Swiss scientist" , "See fifty three across" , "Eighteen-hole game" , "calculating foreigner" .)

I've seen this clue in The Times.

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