City cold: greeting Charlie an effort (7)
I believe the answer is:
chicago
'city' is the definition.
(Chicago is an example)
'cold greeting charlie an effort' is the wordplay.
'cold' becomes 'c' (eg on taps).
'greeting' becomes 'hi' (hi is a kind of greeting).
'charlie' becomes 'c' (phonetic alphabet: alpha, bravo, charlie etc.).
'an' becomes 'a'.
'effort' becomes 'go' (go is a kind of effort).
'c'+'hi'+'c'+'a'+'go'='CHICAGO'
(Other definitions for chicago that I've seen before include "Musical (in Illinois?)" , "Type of bridge" , "1970s' John Kander/Fred Ebb musical" , "Illinois port" , "US city - musical featuring All That Jazz" .)