The early morning air? (4,6)
I believe the answer is:
dawn chorus
'the early morning air?' is the definition.
The definition suggests a singular noun which matches the answer.
'early morning air?' is the wordplay.
'early morning' becomes 'dawn' (I've seen this before).
'air?' becomes 'chorus' (I can't justify this - if you can you should give a lot more credence to this answer).
'dawn'+'chorus'='DAWN CHORUS'
Can you help me to learn more?
(Other definitions for dawn chorus that I've seen before include "Early bird song" , "singing, naturally" , "Early sound of birds" , "Birdsong" , "early music?" .)