Auntie's daughters (6)
I believe the answer is:
nieces
'auntie's daughters' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for nieces that I've seen before include "Relatives of 27dn" , "Relations" , "They're related" , "They're family" , "Scene I set up for relatives" .)