Small turtle leaving soft ground (7)
I believe the answer is:
terrain
'ground' is the definition.
(terrain is land or ground)
'small turtle leaving soft' is the wordplay.
'small turtle' becomes 'terrapin' (I've seen this before).
'leaving' suggests deleting specific letters.
'soft' becomes 'p' (musical abbreviation for 'piano', soft).
'terrapin' with 'p' taken out is 'TERRAIN'.
(Other definitions for terrain that I've seen before include "country" , "Landscape" , "Land (as base for action)" , "Land (viewed tactically)" , "Topography" .)