Gentle sheen or soft glow (6)
I believe the answer is:
lustre
This clue is a double definition.
'gentle sheen' is the first definition.
(I've seen this before)
'soft glow' is the second definition.
(I've seen this before)
(Other definitions for lustre that I've seen before include "Gentle sheen/glow" , "Soft brightness or glory" , "Period" , "Gloss, sheen" , "Gentle sheen, soft glow" .)