Fertile soil (4)
I believe the answer is:
loam
'fertile soil' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for loam that I've seen before include "Rich soil containing decayed matter" , "Rich soil consisting of a mixture of sand, clay and decaying organic materials" , "A rich fertile soil" , "Type of soil" , "Rich soil, good for growing" .)