Omits to sleep surrounded by hissing noises (5)
I believe the answer is:
skips
'omits' is the definition.
(skipping is a kind of omiting)
'sleep surrounded by hissing noises' is the wordplay.
'sleep' becomes 'kip' (synonyms).
'surrounded by' indicates putting letters inside.
'hissing noises' becomes 'ss' (I am not sure about this - if you are sure you should believe this answer much more).
'kip' placed within 'ss' is 'SKIPS'.
'to' is the link.
Can you help me to learn more?
(Other definitions for skips that I've seen before include "Waste containers" , "Large containers for rubbish" .)