Mystical glow (4)
I believe the answer is:
aura
'mystical glow' 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 "Emanation - distinctive air" , "Nimbus" , "Particular ambience" , "Atmosphere, quality" , "Characteristic air of person" .)