Reveal where learner truant in school? (4)

I believe the answer is:

eton

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'school?' is the definition.
(famous UK public school)

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

(Other definitions for eton that I've seen before include "Famous English public school" , "English college of note" , "Kind of collar or jacket (worn at college?)" , "Posh British public school" , "Berkshire public school" .)

I've seen this clue in The Sun and The Telegraph.

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