Charlie greeting character from abroad (3)
I believe the answer is:
chi
'character from abroad' is the definition.
(Greek letter)
'charlie greeting' is the wordplay.
'charlie' becomes 'c' (phonetic alphabet: alpha, bravo, charlie etc.).
'greeting' becomes 'hi' (hi is a kind of greeting).
'c'+'hi'='CHI'
(Other definitions for chi that I've seen before include "seen in Greek writing" , "Greek letter; force in Chinese philosophy" , "Twenty-second Greek letter" , "Classical symbol" , "Greek character" .)