Heathland (4)
I believe the answer is:
moor
'heathland' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for moor that I've seen before include "Ilkley or Bodmin" , "Upland tract - eg Othello" , "Open upland; tie up boat" , "North African - secure a boat - tract of land" , "Berth, tie up" .)