Native abroad heading for mountainous country (7)
I believe the answer is:
'country' is the definition.
(I know that Vietnam is a country)
'native abroad heading for mountainous' is the wordplay.
'abroad' is an anagram indicator.
'heading for' suggests taking the first letters.
The first letter of 'mountainous' is 'm'.
'native' is an anagram of 'vietna'.
(Other definitions for vietnam that I've seen before include "East Asian country" , "country abroad" , "Far Eastern country" , "Country at war with itself from the 1950s to 1970s" , "The dong its currency" .)