Suppress onset of laughter in unfamiliar setting (8)
I believe the answer is:
strangle
'suppress' is the definition.
(I've seen this before)
'onset of laughter in unfamiliar setting' is the wordplay.
'onset of' says to take the initial letters.
'in' is an insertion indicator.
'unfamiliar setting' becomes 'strange'.
The initial letter of 'laughter' is 'l'.
'l' inserted inside 'strange' is 'STRANGLE'.
(Other definitions for strangle that I've seen before include "Tanglers who suffocate" , "Finish off" , "Suppress (an impulse)" , "Smother" , "Tanglers - asphyxiate them" .)