Subtle emanation (4)
I believe the answer is:
aura
'subtle emanation' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for aura that I've seen before include "Perception of distinctive personality" , "Intangible essence emanating from a person" , "Intangible quality surrounding a person or thing" , "Glorious glow" , "distinctive impression" .)