Plane crashed in mountainous country (5)
'mountainous country' is the definition.
(I've seen this before)
'plane crashed' is the wordplay.
'crashed' indicates an anagram.
'plane' with letters rearranged gives 'NEPAL'.
'in' acts as a link.
(Other definitions for nepal that I've seen before include "Mountainous country", "mountainous area", "Himalayan kingdom", "Gurkhas' homeland", "neighbour of Tibet".)