A tittering laugh (3-3)
I believe the answer is:
tee-hee
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">a tittering laugh</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for tee-hee that I've seen before include "Derisive giggle" , "laughing sound" , "Sound of a titter" , "Titter, giggle" , "A tittering laugh" .)