Head examiner putting last of children in jail (4)
I believe the answer is:
jung
'head examiner' is the definition.
(Carl Jung, psychiatrist or examiner of heads)
'last of children in jail' is the wordplay.
'last of' indicates one should take the final letters.
'in' means one lot of letters goes inside another.
'jail' becomes 'jug' ('jug' can be a synonym of 'jail'**).
The last letter of 'children' is 'n'.
'n' placed inside 'jug' is 'JUNG'.
'putting' is the link.
(Other definitions for jung that I've seen before include "Swiss psychologist, Carl" , "Freud's collaborator" , "Swiss psychologist, 1875-1961" , "Swiss psychiatrist" , "Carl --, psychoanalyst" .)