Female voice with ideal tonal qualities (4)
I believe the answer is:
alto
'female voice' is the definition.
(I've seen this in another clue)
'with ideal tonal qualities' is the wordplay.
'with' indicates a hidden word.
'ALTO' can be found hidden inside 'ideal tonal qualities'.
(Other definitions for alto that I've seen before include "Unisex vocal range" , "Second of four parts (in singing)" , "Singing voice between tenor and soprano" , "High male singing voice" , "The highest adult male singing voice" .)