Presence of soldiers surrounding island (4)
I believe the answer is:
mien
'presence' is the definition.
(I know that presence can be written as mien)
'soldiers surrounding island' is the wordplay.
'soldiers' becomes 'men' (men can mean a group of soldiers).
'surrounding' indicates putting letters inside.
'island' becomes 'i' (geographical abbreviation).
'men' placed around 'i' is 'MIEN'.
'of' acts as a link.
(Other definitions for mien that I've seen before include "(One's) manner, bearing" , "Person's bearing" , "Comportment" , "Personal bearing" , "aspect" .)