Boofhead leaving sundries? Affirmative! (3)

I believe the answer is:

yes

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'affirmative' is the definition.
(affirmative answer word)

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

(Other definitions for yes that I've seen before include "I agree" , "Agreed" , "Indeed" , "Of course" , "Validating vote" .)

I've seen this clue in the Sydney Morning Herald.

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