Needle; mountain ridge (4)
I believe the answer is:
spur
I believe this clue is a double definition.
'needle' is the first definition.
(thesaurus)
'mountain ridge' is the second definition.
(I've seen this in another clue)
(Other definitions for spur that I've seen before include "Device to urge on a horse" , "Goad as for a horse" , "Encourage" , "side road" , "Egg on or goad as horseman might" .)