Oppose others surrounding island (6)
I believe the answer is:
resist
'oppose' is the definition.
(resisting is a kind of opposing)
'others surrounding island' is the wordplay.
'others' becomes 'rest' (I've seen this before**).
'surrounding' is an insertion indicator.
'island' becomes 'is'.
'rest' placed around 'is' is 'RESIST'.
(Other definitions for resist that I've seen before include "Fight back" , "Take stand against, oppose" , "Withstand, struggle against" , "Put up fight, oppose forcefully" , "Refuse to comply" .)