Coming down to provide illumination (8)
I believe the answer is:
lighting
I believe this is a double definition.
'coming down' is the first definition.
(lighting is a kind of coming down)
'illumination' is the second definition.
(lighting is a kind of illumination)
'to provide' is the link.
(Other definitions for lighting that I've seen before include "See 14" , "Visual aids" , "landing" , "Illumination" , "What bulbs can provide" .)