US soldier back visiting a second friend from abroad (5)
I believe the answer is:
amigo
'friend from abroad' is the definition.
('friend' in Spanish)
'us soldier back visiting a second' is the wordplay.
'us soldier' becomes 'gi' (informal term for a US soldier).
'back' is a reversal indicator.
'visiting' is an insertion indicator.
'second' becomes 'mo' (both are short periods of time).
'gi' written backwards gives 'ig'.
'a'+'mo'='amo'
'ig' placed inside 'amo' is 'AMIGO'.
(Other definitions for amigo that I've seen before include "Friend in Spanish-speaking area" , "A Spanish pal" , "Foreign ally" , "A Mexican pal" , "Friend from Spain?" .)