Teacher's sound of disapproval, getting zero response at first (5)
I believe the answer is:
tutor
'teacher's' is the definition.
(tutor is a kind of teacher)
'sound of disapproval getting zero response at first' is the wordplay.
'sound of disapproval' becomes 'tut' (I've seen this before).
'getting' is a charade indicator (letters next to each other).
'zero' becomes 'o'.
'at first' suggests taking the first letters.
The first letter of 'response' is 'r'.
'tut'+'o'+'r'='TUTOR'
(Other definitions for tutor that I've seen before include "Guardian" , "Mentor" , "Teach" , "train" , "trainer" .)