Compass for the mountains (5)
I believe the answer is:
range
I believe this clue is a double definition.
'compass' is the first definition.
(I know that compass can be written as range)
'the mountains' is the second definition.
(range of mountains)
'for' acts as a link.
(Other definitions for range that I've seen before include "Mountain stretch" , "Breadth (of variation)" , "spectrum" , "Limit of effectiveness" , "Span" .)