School’s staff mostly blunt about a head (8)
I believe the answer is:
teachers
'school's staff' is the definition.
(teachers work in schools)
'mostly blunt about a head' is the wordplay.
'mostly' means to remove the last letter (most but not all of the word).
'blunt' becomes 'terse' (I've seen this in another clue).
'about' means one lot of letters goes inside another.
'a head' becomes 'each' (as in a phrase like '50 a head').
'terse' with its last letter removed is 'ters'.
'ters' enclosing 'each' is 'TEACHERS'.
(Other definitions for teachers that I've seen before include "Lecturers" , "Instuctors" , "They impart knowledge" , "Pedagogues" , "Instructors" .)