Emit light, shine (4)
I believe the answer is:
glow
I believe this is a double definition.
'emit light' is the first definition.
(glowing is a kind of emiting light)
'shine' is the second definition.
(synonyms)
(Other definitions for glow that I've seen before include "Brightness" , "Radiate or redden" , "Shine, maybe in dark" , "Emanate light" , "Give out light without flames" .)