Maybe demonic look causes damage? (6)
I believe the answer is:
impair
'damage' is the definition.
(I know that impair is a more specific form of damage)
'maybe demonic look' is the wordplay.
'maybe demonic' becomes 'imp' (I am not sure about this - if you are sure you should believe this answer much more).
'look' becomes 'air' (something might have a certain air or look).
'imp'+'air'='IMPAIR'
'causes' acts as a link.
Can you help me to learn more?
(Other definitions for impair that I've seen before include "Hurt or handicap" , "Cause weakening of, damage" , "Damage or handicap" , "Spoil, degrade" , "Hinder" .)