Cool retro case for AirPods (4)

I believe the answer is:

okra

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'cool' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.

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

Can you help me to learn more?

(Other definitions for okra that I've seen before include "old ladies' fingers" , "Lady's fingers; gumbo; bhindi" , "Bhindi in Ind. cookery" , "vegetable soup ingredient" , "Pod eaten in soups, stews etc" .)

I've seen this clue in The Guardian.

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