It's good as hot air (3)

I believe the answer is:

gas

'hot air' is the definition.
(I've seen this in another clue)

'it's good as' is the wordplay.
'it's good' becomes 'g' (abbreviation).
'g'+'as'='GAS'

(Other definitions for gas that I've seen before include "It's not liquid or solid, like American petrol" , "Chatter (colloq.)" , "Hydrogen, for example" , "Petrol (US)" , "idle chit-chat" .)

I've seen this clue in the Evening Standard.

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