Spooky condition (8)
I believe the answer is:
eeriness
'spooky condition' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for eeriness that I've seen before include "Ghostly quality" , "'Weirdness, scariness (8)'" , "Is serene (anag.)" , "Weird quality" , "Horror movie featuring such" .)