Wear away, as soil (5)
I believe the answer is:
erode
'wear away as soil' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for erode that I've seen before include "go to pieces!" , "Gradually wear away" , "'Deteriorate, wear away (5)'" , "Abrade" , "Become ground down or deteriorate" .)