Venerable Asian teacher returned greeting (5)
I believe the answer is:
rishi
'venerable asian' is the definition.
(Sanskrit term for a sage)
'teacher returned greeting' is the wordplay.
'teacher' becomes 'sir' (way of addressing a male teacher).
'returned' says the letters should be written in reverse.
'greeting' becomes 'hi' (hi is a kind of greeting).
'sir' reversed gives 'ris'.
'ris'+'hi'='RISHI'
(Other definitions for rishi that I've seen before include "Revered man" , "wise man" , "Guru" , "holy man" , "Poet" .)