Good soil (4)
I believe the answer is:
loam
'good 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 with decayed vegetable matter" , "Rich soil, good for growing" , "Type of soil" , "A rich fertile soil" , "Rich soil containing decayed matter" .)