Wet soft earth (3)
I believe the answer is:
mud
'wet soft earth' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for mud that I've seen before include "Muck - actionable remarks" , "Here's . . . in your eye - it's a toast" , "damaging allegations" , "Liquid earth" , "Alluvial deposit as in river bed" .)