High grade given by teacher having retired (4)
I believe the answer is:
abed
'having retired' is the definition.
(I've seen this before)
'high grade given by teacher' is the wordplay.
'high grade' becomes 'A' (academic grade).
'given by' is a charade indicator (letters next to each other).
'teacher' becomes 'bed' (holder of a BEd, Bachelor of Education degree).
'a'+'bed'='ABED'
(Other definitions for abed that I've seen before include "going to sleep?" , "in a comfortable position" , "Not yet up (archaic)" , "Possibly sleeping" , "Sleeping (archaic)" .)