What's loud has listener showing anxiety (4)
I believe the answer is:
fear
'anxiety' is the definition.
(I know that fear is a type of anxiety)
'what's loud has listener' is the wordplay.
'what's loud' becomes 'f' (short for forte - 'loud' in music).
'has' is a charade indicator (letters next to each other).
'listener' becomes 'ear' (body part which hears or listens).
'f'+'ear'='FEAR'
'showing' is the link.
(Other definitions for fear that I've seen before include "awe" , "Dread, great anxiety" , "Feeling of dread" , "Cutting edge" , "Dread, alarm" .)