Teacher back in Paris (3)
I believe the answer is:
sir
'teacher' is the definition.
(way of addressing a male teacher)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for sir that I've seen before include "Poet and novelist" , "Gentleman's form of address" , "address to teacher" , "Male title of respect" , "... ___ John Major" .)