A quiet chum joining a Greek character at a US location (10)
I believe the answer is:
appalachia
'a us location' is the definition.
(region of the USA)
'a quiet chum joining a greek character' is the wordplay.
I cannot really see how this works, but
'a' is found in the answer.
'quiet' could be 'pp' (musical abbreviation for pianissimo) and 'pp' is present in the answer.
'character' could be 'chi' (chi is a kind of character) and 'chi' is found in the answer.
This explanation may well be incorrect...
'at' acts as a link.
(Other definitions for appalachia that I've seen before include "American region" , "US mountain region" , "Mountainous region of eastern USA" , "US mining area" , "Area of eastern US" .)