Not a true tot, anyhow; just a high voice (8)
I believe the answer is:
falsetto
'high voice' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for falsetto that I've seen before include "Unnaturally high voice" , "Artificial upper register of a male voice" , "A forced high singing voice" , "Abnormally high voice" , "Forcedly high voice" .)