One might hang on until it gets warmer (6)

I believe the answer is:

icicle

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'one' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for icicle that I've seen before include "Frozen water-drips" , "Hanging ice spike" , "Something hanging in winter" , "Frozen water drops" , "this tapers" .)

I've seen this clue in The Telegraph.

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