Flag initially identified by retired teacher? (4)
I believe the answer is:
iris
'flag' is the definition.
('iris' can be a synonym of 'flag')
'initially identified by retired teacher?' is the wordplay.
'initially' suggests taking the first letters.
'by' says to put letters next to each other.
'retired' says the letters should be written in reverse.
'teacher?' becomes 'sir' (I've seen this before**).
The first letter of 'identified' is 'i'.
'sir' back-to-front is 'ris'.
'i'+'ris'='IRIS'
(Other definitions for iris that I've seen before include "Goddess of the rainbow in the eye" , "Flower and eye membrane" , "may open up in camera" , "Nice flower or eye part" , "Woman" .)