Half sodden piece of turf (3)
I believe the answer is:
sod
'piece of turf' is the definition.
(I've seen this in another clue)
'half sodden' is the wordplay.
'half' suggests halving the letters.
'sodden' halved is 'SOD'.
(Other definitions for sod that I've seen before include "A piece of sward." , "'Sward, turf (3)'" , "Surface layer of ground with grass roots" , "Piece of peat or grass" , "Lump of earth" .)