One sustained by so much hot air? (7)

I believe the answer is:

balloon

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'one sustained by so much hot air?' is the definition.
The definition and answer can be both related to change as well as being verbs in their base form.
Maybe they are linked in a way I don't understand?

This is the entire clue.

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(Other definitions for balloon that I've seen before include "One blown up for party" , "Inflatable sphere, may contain hot air" , "Inflatable - rapidly expand" , "Inflate" , "Inflatable rubber bag, could be filled with hot air" .)

I've seen this clue in the Evening Standard.

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