What it is when there’s a bite in the air (5)

I believe the answer is:

nippy

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'air' is the definition.
Both the answer and definition are adjectives. Perhaps you can see an association between them that I don't see?

I can't explain the remainder of the clue.

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(Other definitions for nippy that I've seen before include "active" , "Slightly cold?" , "A bit cold?" , "Able to move quickly" , "Speedy - cold" .)

I've seen this clue in the Evening Standard.

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