Mother's sisters (5)
I believe the answer is:
aunts
'mother's sisters' 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" , "Relatives get a peculiar US tan" , "Female relatives, usually older" , "Parents' sisters" , "Relatives get an odd US tan" .)