Light discharge (4)
I believe the answer is:
fire
I believe this clue is a double definition.
'light' is the first definition.
(thesaurus)
'discharge' is the second definition.
('fire' can be a synonym of 'discharge')
(Other definitions for fire that I've seen before include "Sack; conflagration" , "Flames; passion" , "Flame - dismiss - shoot" , "Dismiss; bake in a kiln" , "Manually operated device for dealing with flames" .)