Yard covering (4)
(Other definitions for lawn that I've seen before include "Grassy expanse" , "Type of thin linen or cotton" , "Cultivated and mown grass" , "material" , "Green area" .)
(Other definitions for grass that I've seen before include "Pasturage" , "Rat" , "blades" , "Reefer's content" , "blow the gaff" .)