Shocked; horrified (6)
I believe the answer is:
aghast
This clue is a double definition.
'shocked' is the first definition.
(synonyms)
'horrified' is the second definition.
(I've seen this before)
(Other definitions for aghast that I've seen before include "struck with fear" , "Taken aback with horror" , "Deeply dismayed" , "Horrified, filled iwth consternation" , "Confounded" .)