Duke seen by family members is intimidating (6)
I believe the answer is:
daunts
'is intimidating' is the definition.
'duke seen by family members' is the wordplay.
'duke' becomes 'd' (abbreviation).
'seen by' is a charade indicator (letters next to each other).
'family members' becomes 'aunts' (I've seen this in another clue).
'd'+'aunts'='DAUNTS'
(Other definitions for daunts that I've seen before include "Makes afraid or discouraged" , "Cows" , "Frightens or discourages" , "intimidates" .)