An untruth to gain entry as a foreigner (5)
I believe the answer is:
alien
'a foreigner' is the definition.
('alien' can be a synonym of 'foreigner')
'an untruth to gain entry' is the wordplay.
'an' becomes 'a'.
'untruth' becomes 'lie' (lie is a kind of untruth).
'to gain entry' becomes 'n' (I can't justify this - if you can you should give a lot more credence to this answer).
'a'+'lie'+'n'='ALIEN'
'as' is the link.
Can you help me to learn more?
(Other definitions for alien that I've seen before include "Foreign; extraterrestrial" , "Foreign, strange" , "of foreigners" , "coming from overseas" , "Belonging to a foreign country" .)