Sound of disapproval in institute (3)
I believe the answer is:
tut
'sound of disapproval' is the definition.
(I've seen this before)
'in institute' is the wordplay.
'in' says the answer is hidden in the clue.
'TUT' is hidden in the letters of 'institute'.
(Other definitions for tut that I've seen before include "Express disapproval" , "Disapproving comment" , "Noise of disapproval" , "King wrapped up" , "King exhumed" .)