Completely understand the woman's missing voice (4)
I believe the answer is:
alto
'voice' is the definition.
(alto is a kind of voice)
I don't understand the rest of the clue.
(Other definitions for alto that I've seen before include "Key old > male who scores high" , "Highest male voice: lowest female voice" , "A singing voice or pitch" , "Singing range" , "Member of choir" .)