Mystical emanation (4)
I believe the answer is:
aura
'mystical emanation' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for aura that I've seen before include "Particular ambience" , "Emanation - distinctive air" , "Characteristic air of person" , "Intangible atmosphere" , "'Air, atmosphere (4)'" .)