Express derision (4)
I believe the answer is:
jeer
'express derision' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for jeer that I've seen before include "Call out derisively" , "Scoff, deride, mock" , "Rudely mocking remark" , "Tease" , "Boo" .)