Elsa's sister (4)
I believe the answer is:
anna
'elsa's sister' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for anna that I've seen before include "Girl - old Indian coin" , "Old foreign coin" , "Girl's name (palindrome)" , "Miss Karenina" , "- - Ford (TV)" .)