Wicked light (6)
I believe the answer is:
candle
'wicked light' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for candle that I've seen before include "something wicked" , "It's better to light one than curse the darkness, it's said" , "that's wicked!" , "Measurement of light" , "Artificial light" .)