Booze trashed what's within school walls (7)

I believe the answer is:

alcohol

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'booze' is the definition.
(I know that booze can be written as alcohol)

I can't explain the rest of the clue.

(Other definitions for alcohol that I've seen before include "Intoxicant fluid" , "The intoxicant in drink" , "Intoxicant in wine, etc." , "Intoxicating element of liquor" , "John Barleycorn" .)

I've seen this clue in The Guardian.

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