Abby's twin (3)
I believe the answer is:
ann
'abby's twin' 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 "... Margret or Hathaway" , "eg Miss Widdecombe" , "female" , "... -Margaret (film actress)" , "- Widdecombe MP" .)