Heath to tie boat up (4)
I believe the answer is:
moor
'heath' is the definition.
(both can mean a type of landscape)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for moor that I've seen before include "Heathland" , "Tract of uncultivated upland" , "Open land covered with heather and bracken" , "Heath - a North African Muslim" , "Securely fix" .)