Obscures (7)
'obscures' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for darkens that I've seen before include "becomes gloomy" , "Gets black" .)
(Other definitions for shrouds that I've seen before include "Winding-sheets" , "Burial garments" , "Wrappers for corpses" .)