That girl who goes to bat in a bikini? (3)
I believe the answer is:
her
'that girl' is the definition.
('her' refers to a girl or woman)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for her that I've seen before include "The female's" , "She, objectively" , "Belonging to a female" , "Pronoun used of ship" , "In the Midlands she" .)