Mystical, supernatural (6)
I believe the answer is:
occult
I believe this clue is a double definition.
'mystical' is the first definition.
(I know that mystical can be written as occult)
'supernatural' is the second definition.
(I know that supernatural can be written as occult)
(Other definitions for occult that I've seen before include "Magical; secret" , "Involving supernatural phenomena" , "Involving magical powers" , "Esoteric, magical" , "Supernatural forces and events and beings" .)