Young lady ignoring large fool (3)

I believe the answer is:

ass

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'fool' is the definition.
(both can mean a stupid person)

I can't explain the remainder of the clue.

(Other definitions for ass that I've seen before include "Braying animal" , "Dolt" , "Charlie" , "Dipstick" , "Pompous person" .)

I've seen this clue in The Times.

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