Take legal case against girl (3)
I believe the answer is:
sue
This clue is a double definition.
'take legal case against' is the first definition.
(I've seen this before)
'girl' is the second definition.
(girl's name)
(Other definitions for sue that I've seen before include "Bring charges against - girl" , "Make a legal claim" , "Take a casa against (3)" , "Susan (dim.)" , "Begin legal proceedings against" .)