Gardener's soil
I believe the answer is:
loam
'gardener's 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 consisting of a mixture of sand, clay and decaying organic materials" , "Rich soil with decayed vegetable matter" , "Rich soil, good for growing" , "Type of soil" , "Rich soil containing decayed matter" .)