Luminous glow (4)
I believe the answer is:
aura
'luminous glow' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for aura that I've seen before include "Supposed emanation surrounding the body" , "Distinct but intangible quality about a person" , "Emanation - distinctive air" , "Distinctive character, essence of a living thing" , "Characteristic air of person" .)