Stare in astonishment (4)
I believe the answer is:
gape
'stare in astonishment' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for gape that I've seen before include "Open-mouthed stare" , "Peer" , "Failure to meet" , "Hang wide open" , "watch in wonder" .)