Dishearten daughter and dad's sister (5)
I believe the answer is:
daunt
'dishearten' is the definition.
(I've seen this in another clue)
'daughter and dad's sister' is the wordplay.
'daughter' becomes 'd' (genealogical abbreviation).
'and' is a charade indicator (letters next to each other).
'dad's sister' becomes 'aunt' (I've seen this in another clue).
'd'+'aunt'='DAUNT'
(Other definitions for daunt that I've seen before include "Make to feel intimidated" , "Make (someone) apprehensive" , "Scare off - dismay" , "Cause to feel intimidated" , "Dishearten" .)