Public sale brings university into battle (7)

I believe the answer is:

auction

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'public sale' is the definition.
(sale of items to the public)

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

(Other definitions for auction that I've seen before include "Public sale by bid" , "Lots are sold here!" , "Caution about method of sale" , "Public sale with lots" , "Use caution at public sale" .)

I've seen this clue in The Sun.

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