Half-suppressed laugh (6)
I believe the answer is:
titter
'half-suppressed laugh' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for titter that I've seen before include "Nervous or affected laugh" , "Stifled laugh" , "Suppressed snigger" , "Laugh nervously in high-pitched way" , "Half-suppressed laugh" .)