Abby's sister (3)
I believe the answer is:
ann
'abby's sister' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ann that I've seen before include "Lady's name" , "female" , "... -Margaret (film actress)" , "- - Jones, 1969 Wimbledon champion" , "... Margret or Hathaway" .)