Dad's sister (4)
I believe the answer is:
'dad's sister' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for aunt that I've seen before include "Sister of father/mother" , "Charley's ___ , farce staged in London in 1892, revived and adapted ever since" , "Family member" , "Female relation" , "kinswoman" .)