Opposed by those resolved to protect the borders of Israel (7)
I believe the answer is:
hostile
'opposed' is the definition.
('hostile' can be similar in meaning to 'opposed')
'those resolved to protect the borders of israel' is the wordplay.
'resolved' is an anagram indicator.
'to protect' indicates putting letters inside.
'the borders of' says to hollow out the word (remove centre letters).
'israel' with its centre taken out is 'il'.
'those' with letters rearranged gives 'hoste'.
'hoste' going around 'il' is 'HOSTILE'.
'by' is the link.
(Other definitions for hostile that I've seen before include "Inimical" , "Unkind" , "Antagonistic" , "Aggressive" , "Enemy" .)