Greek character’s cold greeting (3)
I believe the answer is:
chi
'greek character's' is the definition.
(letter from the Greek alphabet)
'cold greeting' is the wordplay.
'cold' becomes 'c' (eg on taps).
'greeting' becomes 'hi' (hi is a kind of greeting).
'c'+'hi'='CHI'
(Other definitions for chi that I've seen before include "Mental projection" , "Greek letter; force in Chinese philosophy" , "The life force, according to traditional Chinese medicine" , "Chinese life-force" , "T'ai -, martial art" .)