Not a girl’s full name (4)
I believe the answer is:
demi
'not a' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.
'girl's full name' is the wordplay.
I cannot quite understand how this works, but
'name' could be 'em' and 'em' is found within the answer.
'girl' could be 'di' and 'di' is found within the leftover letters.
No letters remain.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for demi that I've seen before include "Prefix for half or part" , "-- Moore, actress" , "Half-sized" , "Half for a dime" .)