Installs, as a lawn (4)
I believe the answer is:
sods
'installs as a lawn' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sods that I've seen before include "sort of law" , "Lumps of earth" , "Lumps of turf" , "Turves" , "Unpleasant people" .)