It fills Antarctic expanses (3)

I believe the answer is:

ice

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

'it fills' is the definition.
The definition suggests a singular noun which matches the answer.

'antarctic expanses' is the wordplay.
'ICE' is hidden within the letters.
However, I'm uncertain how this is indicated.

Can you help me to learn more?

(Other definitions for ice that I've seen before include "Chill - harden" , "Formality" , "Cooler" , "Solid water" , "Top cake" .)

I've seen this clue in The Independent.

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