Silly sketch Rembrandt initially discarded (4)

I believe the answer is:

daft

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'silly' is the definition.
(I've seen this in another clue)

I can't explain the remainder of the clue.

(Other definitions for daft that I've seen before include "Potty" , "like a brush?" , "Informally crazy as a brush" , "Bats!" , "Stupid" .)

I've seen this clue in The Times.

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