Article thanks to foreign character (5)
I believe the answer is:
theta
'foreign character' is the definition.
(Greek letter)
'article thanks' is the wordplay.
'article' becomes 'the' (the definite article in English).
'thanks' becomes 'ta' (UK informal version of 'thank you').
'the'+'ta'='THETA'
'to' acts as a link.
(Other definitions for theta that I've seen before include "letter from abroad" , "Homeric character" , "8th letter of the Greek alphabet" , "Letter from Greece" , "Make amends for" .)