How the unwelcoming Jack spoke? (8)

I believe the answer is:

frostily

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'how' is the definition.
Both the definition and answer are adverbs. Maybe you can see an association between them that I don't see?

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for frostily that I've seen before include "How Jack may behave" , "in an aloof manner?" .)

I've seen this clue in the Evening Standard.

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