Island needs new rescue arranged for vulnerable (8)
I believe the answer is:
insecure
'vulnerable' is the definition.
(similar in meaning)
'island needs new rescue arranged' is the wordplay.
'island' becomes 'i' (geographical abbreviation).
'needs' means one lot of letters go next to another.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'arranged' is an anagram indicator (letters rearranged).
'rescue' anagrammed gives 'secure'.
'i'+'n'+'secure'='INSECURE'
'for' is the link.
(Other definitions for insecure that I've seen before include "Wavering" , "Vulnerable" , "Timid" , "Dangerous" , "Sinecure for those lacking in confidence" .)