Buffoon Jack's unsettled by unknown kitchen utensil (6)

I believe the answer is:

zester

I'm a little stuck... Click here to teach me more about this clue!

'kitchen utensil' is the definition.
(I've seen this before)

I don't understand the rest of the clue.

(Other definitions for zester that I've seen before include "kitchen utensil" , "rubbing off on Clementine?" , "Orange/lemon peel scraper" , "Kitchen assistant" .)

I've seen this clue in The Telegraph.

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