Struck with amazement (6)
I believe the answer is:
aghast
'struck with amazement' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for aghast that I've seen before include "Stupefied with horror" , "Taken aback with horror" , "Filled with horror or shock" , "Shocked, dumbfounded" , "'Horrified, shocked (6)'" .)