Reason soil broken up (6)
I believe the answer is:
ground
I believe this is a triple definition!
'reason' is the first definition.
(I know that reason can be written as ground)
'soil' is the second definition.
(synonyms)
'broken up' is the third definition.
(grinding is a kind of breaking up)
(Other definitions for ground that I've seen before include "territory" , "what coffee might be" , "broken into small particles" , "turned to dust" , "crumbled" .)