Greek letter's about right boy or girl (5)
I believe the answer is:
chris
'girl' is the definition.
'greek letter's about right' is the wordplay.
'greek letter's' becomes 'chi's' (letter from the Greek alphabet).
'about' indicates putting letters inside.
'right' becomes 'r' (common abbreviation).
'chis' enclosing 'r' is 'CHRIS'.
'boy or' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for chris that I've seen before include "Diminutive male or female name" , "-- Bonington, British mountaineer" , "-- Martin, Coldplay lead singer" .)