Airy talk (3)
I believe the answer is:
gas
'talk' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for gas that I've seen before include "person who's amusing ..." , "Talk profusely" , "Carbon dioxide, say" , "Form of fossil fuel" , "Oxygen is one" .)