A head seen among teachers (4)
I believe the answer is:
each
'a head' is the definition.
(I've seen this before)
'among teachers' is the wordplay.
'among' indicates the answer is hidden within the clue.
'EACH' is hidden in the letters of 'teachers'.
'seen' acts as a link.
(Other definitions for each that I've seen before include "every one individually" , "Every one separately" , "Every one of a number" , "Everyone separately" , "every one of a group" .)