Duck carried in evil air (5)
I believe the answer is:
voice
'air' is the definition.
(voice is a kind of air)
'duck carried in evil' is the wordplay.
'duck' becomes 'o'.
'carried in' means one lot of letters goes inside another.
'evil' becomes 'vice' (vice is a kind of evil).
'o' placed within 'vice' is 'VOICE'.
(Other definitions for voice that I've seen before include "Sound produced by humans" , "Give expression to" , "Power of speech" , "Sound with which one speaks" , "Utter - part" .)