Cry of surprise initially falling upon island (5)
I believe the answer is:
corfu
'island' is the definition.
(Greek island)
'cry of surprise initially falling upon' is the wordplay.
'cry of surprise' becomes 'cor' (colloquial).
'initially' says to take the initial letters.
The initial letters of 'falling upon' is 'fu'.
'cor'+'fu'='CORFU'
(Other definitions for corfu that I've seen before include "part of Greece" , "holiday venue!" , "Gk. island, opposite Albania" , "Popular holiday island off West Greece" , "Holiday location" .)