Lump of earth (4)
I believe the answer is:
clod
'lump of earth' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for clod that I've seen before include "'Clump, glob (4)'" , "Silly person" , "Clump - chump" , "Compact mass - stupid person" , "Idiot" .)