Syllable of disapproval (3)
![Ross](/clue/static/ross-mug.min.png)
'syllable of disapproval' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for tut that I've seen before include "Express disapproval" , "Disapproving comment" , "Annoyed exclamation" , "in short I don't like that!" , "Sound of mild disapproval" .)