Mother has about six, but only one girl
I believe the answer is:
mavis
'girl' is the definition.
'mother has about six but only one' is the wordplay.
'mother' becomes 'ma' (ma can mean mother).
'has' means one lot of letters go next to another.
'about six but only one' becomes 'vis' (I can't explain this - if you can you should believe this answer much more).
'ma'+'vis'='MAVIS'
Can you help me to learn more?
(Other definitions for mavis that I've seen before include "bird" , "Fem. name, song thrush" , "Girl" , "Girl's name - song thrush" .)