Jeer, mock (5)
This clue is a double definition.
'jeer' is the first definition.
(I know that jeer can be written as scoff)
'mock' is the second definition.
(scoff can mean to mock or tease)
(Other definitions for scoff that I've seen before include "Jeer - eat quickly" , "Speak contemptuously or drink informally" , "taunt" , "Greedily consume" , "Quickly swallow" .)
This clue is a double definition.
'jeer' is the first definition.
(I've seen this before)
'mock' is the second definition.
(thesaurus)
(Other definitions for hiss that I've seen before include "S-s-snake's s-s-sound?" , "(Make noise to) express disapproval" , "Make disapproving sound" , "Wordless sound of disapproval" , "Sibilant sound made through the teeth" .)