Curious way leading to the mountains (7)
I believe the answer is:
strange
'curious' is the definition.
('strange' can be a synonym of 'curious')
'way leading to the mountains' is the wordplay.
'way' becomes 'st'.
'leading to' means one lot of letters go next to another (some letters go before or lead others).
'the mountains' becomes 'range' (I've seen this before).
'st'+'range'='STRANGE'
(Other definitions for strange that I've seen before include "Queer" , "Extraordinary" , "Funny" , "Foreign" , "Odd or unknown" .)