Sister of Amy, Jo, and Meg (4)
I believe the answer is:
beth
'sister of amy jo and meg' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for beth that I've seen before include "Hebrew letter; girl's name" , "character in Israel" , "letter to the Hebrews" , "Hebrew B" , "Little Women sister" .)