Opening eye initially to stare in wonder (4)
I believe the answer is:
gape
'stare in wonder' is the definition.
(I've seen this before)
'opening eye initially' is the wordplay.
'opening' becomes 'gap' (synonyms).
'initially' suggests taking the first letters.
The first letter of 'eye' is 'e'.
'gap'+'e'='GAPE'
'to' is the link.
(Other definitions for gape that I've seen before include "Yawn" , "Stare with open mouth in wonder" , "Open-mouthed stare" , "Stare at page" , "Look amazed" .)