Letter from Greece, and some from e.g. Argentina (5)
I believe the answer is:
omega
'letter from greece' is the definition.
(letter from the Greek alphabet)
'some from e g argentina' is the wordplay.
'some' indicates a hidden word (some parts of the word are used).
'OMEGA' is hidden within 'from e g argentina'.
'and' acts as a link.
(Other definitions for omega that I've seen before include "Athenian character" , "Final Greek letter" , "letter to Greeks" , "Last (Gk. letter)" , "in Greece, the limit!" .)