Page greeting character from Athens (3)
I believe the answer is:
phi
'character from athens' is the definition.
(letter from the Greek alphabet)
'page greeting' is the wordplay.
'page' becomes 'p'.
'greeting' becomes 'hi' (hi is a kind of greeting).
'p'+'hi'='PHI'
(Other definitions for phi that I've seen before include "Twenty First Greek letter, pronounced as f" , "Greek letter, equivalent to F" , "One Greek" , "Greek letter; sounds like expression of outrage" , "Greek character" .)