Foreigner's story accepted by soldier for the most part (5)
I believe the answer is:
alien
'foreigner's' is the definition.
('alien' can be a synonym of 'foreigner')
'story accepted by soldier for the most part' is the wordplay.
'story' becomes 'lie' (I've seen this before).
'accepted by' indicates putting letters inside.
'soldier' becomes 'ant' (I've seen this before).
'for the most part' means to remove the last letter.
'ant' with its last letter taken off is 'an'.
'lie' put within 'an' is 'ALIEN'.
(Other definitions for alien that I've seen before include "Offensive" , "One is from outer space, perhaps" , "Foreign (from outer space?)" , "ET" , "extraneous" .)