Anxious after a loud assault (6)
I believe the answer is:
afraid
'anxious' is the definition.
(synonyms)
'after a loud assault' is the wordplay.
'after' means one lot of letters go next to another.
'loud' becomes 'f' (short for forte - 'loud' in music).
'assault' becomes 'raid' (I've seen this in another clue).
'a' next to 'f' is 'af'.
'af'+'raid'='AFRAID'
(Other definitions for afraid that I've seen before include "makes one panicky" , "Frightened" , "Feeling anxiety or fear" , "Timorous" , "feeling scared" .)