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' means one lot of letters go next to another.
'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" .)