Downturn concerning hearing, audibly (9)
I believe the answer is:
recession
'downturn' is the definition.
(I've seen this in another clue)
'concerning hearing audibly' is the wordplay.
'concerning' becomes 're' (both can mean on a particular topic).
'hearing' becomes 'session' (I've seen this before).
'audibly' shows a homophone (sound like).
'session' is a homophone of 'cession'.
're'+'cession'='RECESSION'
(Other definitions for recession that I've seen before include "Decline in economic activity and prosperity" , "falling back" , "Down-turn" , "when times are hard" , "Widespread decline in employment and trade" .)