Singer? Get her to quit completely (4)
I believe the answer is:
alto
'singer?' is the definition.
(alto is a kind of singer)
'her to quit completely' is the wordplay.
I cannot really see how this works, but
'to' is found in the answer.
This explanation may well be incorrect...
'get' is the link.
Can you help me to learn more?
(Other definitions for alto that I've seen before include "Singing range" , "Highest male voice: lowest female voice" , "The highest adult male singing voice" , "someone to sing" , "Kind of singing voice, male or female" .)