Fool dropping piano from overture? (3)

I believe the answer is:

ass

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

I don't understand the rest of the clue.

(Other definitions for ass that I've seen before include "A donkey or an idiot" , "Transport for a wise man - or a fool" , "Animal; fool" , "Donkey - one that's foolish" , "animal inside" .)

I've seen this clue in The Independent.

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