Ominous; eerie (8)
I believe the answer is:
sinister
I believe this clue is a double definition.
'ominous' is the first definition.
(I know that ominous can be written as sinister)
'eerie' is the second definition.
(Other definitions for sinister that I've seen before include ", nun going round home" , "'Ominous, baleful (8)'" , "Eerie, alarming" , "Threatening evil on the heraldic left" , "Malign, ominous" .)