Greatly surprised, astonished (6)
I believe the answer is:
amazed
I believe this is a double definition.
'greatly surprised' is the first definition.
(I've seen this before)
'astonished' is the second definition.
(I know that astonished can be written as amazed)
(Other definitions for amazed that I've seen before include "Greatly surprised, never would have thought it" , "knocked for six" , "Flabbergasted" , "was stunning" , "Gobsmacked" .)