Horrified at hags being harassed! (6)
I believe the answer is:
aghast
'horrified' is the definition.
(I know that horrified can be written as aghast)
'at hags being harassed' is the wordplay.
'being harassed' indicates anagramming the letters.
'at'+'hags'='athags'
'athags' is an anagram of 'AGHAST'.
(Other definitions for aghast that I've seen before include "struck with fear" , "Filled with horror or shock" , "Stunned" , "Deeply dismayed" , "Taken aback with horror" .)