Plane crashes in mountainous region (5)
I believe the answer is:
nepal
'mountainous region' is the definition.
(mountainous country in Asia)
'plane crashes' is the wordplay.
'crashes' indicates an anagram.
'plane' is an anagram of 'NEPAL'.
'in' is the link.
(Other definitions for nepal that I've seen before include "World's only Hindu kingdom" , "Himalayan state" , "mountainous area" , "somewhere in Asia" , "Country located mainly in the Himalayas" .)