Patty and Selma, to Bart and Lisa (5)
I believe the answer is:
aunts
'patty and selma to bart and lisa' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for aunts that I've seen before include "Relatives get bad US tan" , "Elderly female relations" , "Female relatives, usually older" , "Sally and others" , "relatively speaking" .)