Ignites or illuminates (6)
I believe the answer is:
lights
I believe this is a double definition.
'ignites' is the first definition.
(lighting is a kind of igniting)
'illuminates' is the second definition.
('light' can be a synonym of 'illuminate')
(Other definitions for lights that I've seen before include "organs" , "Lungs of sheep, pigs etc used as food" , "Offal" , "Ignites or illumines" , "Lamps" .)