Make fast heath (4)
I believe the answer is:
moor
I believe this is a double definition.
'make fast' is the first definition.
(mooring is a kind of making fast)
'heath' is the second definition.
(both can mean a type of landscape)
(Other definitions for moor that I've seen before include "Open land covered with heather and bracken" , "Upland area - tie up" , "See 5 Down" , "Large area of open, uncultivated land" , "'On Ilka - - baht'at'" .)