Coming publicity over an airway (6)
I believe the answer is:
advent
'coming' is the definition.
(advent is the arrival or coming of something)
'publicity over an airway' is the wordplay.
'publicity' becomes 'ad' (short for advert).
'over an airway' becomes 'vent' (I can't explain this - if you can you should believe this answer much more).
'ad'+'vent'='ADVENT'
Can you help me to learn more?
(Other definitions for advent that I've seen before include "Arrival (with calendar?)" , "Christmas shopping time in" , "Time approaching Christmas" , "It's a-coming in December!" , "Coming, arrival" .)