Audible expression of amusement (5)
I believe the answer is:
laugh
'audible expression of amusement' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for laugh that I've seen before include "Cachinnate" , "Make sound expressing amusement" , "Fun person" , "Possible response to joke" , "Audible expression of amusement" .)