Distance to target in the mountains (5)
I believe the answer is:
range
I believe this is a double definition.
'distance to target' is the first definition.
(I've seen this in another clue)
'the mountains' is the second definition.
(range of mountains)
'in' is the link.
(Other definitions for range that I've seen before include "Compass, extent" , "Cooking appliance" , "Wander freely" , "Cut; cultivated plant" , "Aga or mountain, perhaps?" .)