Voice of a boy in a pro's tremulously negative voice (7)
I believe the answer is:
soprano
'voice' is the definition.
(I know that soprano is a type of singing voice)
'a boy in a pro's tremulously negative voice' is the wordplay.
I cannot quite understand how this works, but
'a' could be 'an' and 'an' is found within the answer.
an anagram of 'pro' is 'opr' which is present in the answer.
The remaining letters 'so' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'of' is the link.
Can you help me to learn more?
(Other definitions for soprano that I've seen before include "High singing voice" , "High female voice" , "Female singing voice" , "Female singer" , "Singer of high notes" .)