Derisive sound (5)
I believe the answer is:
snort
'derisive sound' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for snort that I've seen before include "Noisily express indignation" , "Chortle" , "quick drink" , "Make derisive noise" , "Derisive noise made through nose" .)