Foreign character is affectedly stylish? Not half! (3)
I believe the answer is:
chi
'foreign character' is the definition.
(Greek letter)
'affectedly stylish? not half' is the wordplay.
'affectedly stylish?' becomes 'chichi' (I've seen this before).
'not half' suggests halving the letters.
'chichi' with half the letters taken is 'CHI'.
'is' acts as a link.
(Other definitions for chi that I've seen before include "seen in Greek writing" , "Mental projection" , "Greek X" , "Greek letter; force in Chinese philosophy" , "Classical character" .)