Obscured (6)
(Other definitions for dimmed that I've seen before include "Grew less bright" , "Grew fainter" , "Made less bright" , "Lowered in brightness" .)
'obscured' is the definition.
(clouding is a kind of obscuring)
This is the entire clue.
(Other definitions for clouded that I've seen before include "Obscured" , "blurred" , "Sort of leopard" , "-- Leopard; -- yellow" , "Not transparent" .)