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