Area of high level ground (7)
I believe the answer is:
plateau
'area of high level ground' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for plateau that I've seen before include "State of little change after a period of activity" , "Large level tract of elevated land" , "Flat raised land" , "relatively flat territory" , "Paul, eat! (anag)" .)