Lump of earth or clay (4)
I believe the answer is:
clod
This clue is a double definition.
'lump of earth' is the first definition.
(I've seen this before)
'clay' is the second definition.
(thesaurus)
(Other definitions for clod that I've seen before include "Lump of earth - nitwit" , "Fool - bit of turf" , "Block" , "Idiot" , "Stupid person - compact lump" .)