Ground close to swamp passed over by turtle (7)
I believe the answer is:
terrain
'ground' is the definition.
(terrain is land or ground)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for terrain that I've seen before include "Tract of land of a specific character" , "country" , "Tract of land with particular character" , "Area of ground with a particular characteristic" , "Physical feature of a stretch of ground" .)