Disturbance produced by a very loud fish! (6)
I believe the answer is:
affray
'disturbance' is the definition.
(synonyms)
'by a very loud fish' is the wordplay.
'by' says to put letters next to each other.
'very loud' becomes 'ff' (musical abbreviation).
'fish' becomes 'ray' (ray is a kind of fish).
'a' put next to 'ff' is 'aff'.
'aff'+'ray'='AFFRAY'
'produced' acts as a link.
(Other definitions for affray that I've seen before include "Fish; had an odour" , "Breach of the peace; brawl, fight" , "Brawling" , "Brawl, disturbance" , "Noisy quarrel" .)