Hilarity after catching disgusted expression (8)
I believe the answer is:
laughter
'hilarity' is the definition.
(I've seen this before)
'after catching disgusted expression' is the wordplay.
'after' becomes 'later' (I've seen this in another clue).
'catching' is an insertion indicator.
'disgusted expression' becomes 'ugh' (expression of disgust).
'later' placed around 'ugh' is 'LAUGHTER'.
(Other definitions for laughter that I've seen before include "The expression of lively amusement" , "Manifestation of mirth" , "Sound of amusement" , "Hilarity" , "Sound of merriment" .)