Does it float through the air? (8)

I believe the answer is:

seaplane

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

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for seaplane that I've seen before include "Marine aircraft" , "Floating aircraft" .)

I've seen this clue in the Evening Standard.

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