Night demon (7)
I believe the answer is:
incubus
'night demon' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for incubus that I've seen before include "Demon bringing nightmares" , "Burdensome person or evil spirit visiting sleeper" , "Oppressive burden" , "Evil spirit visiting a sleeping person" , "Male demon - nightmare - obsession" .)