Barked in a high-pitched tone (6)
I believe the answer is:
yapped
'barked in a high-pitched tone' is the definition.
('yap' can be a synonym of 'bark in a high-pitched tone')
This is the entire clue.
(Other definitions for yapped that I've seen before include "Barked like a small dog" , "Chatted" , "Yelped" .)