Grassy clump (3)
I believe the answer is:
sod
'grassy clump' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sod that I've seen before include "A piece of sward." , "'Sward, turf (3)'" , "Piece of turf; a Law named for him" , "Piece of peat or grass" , "Surface layer of ground with grass roots" .)