Enemy destroyed island from a peninsula (6)
I believe the answer is:
yemeni
'from a peninsula' is the definition.
(Yemen is part of the Arabian Peninsula)
'enemy destroyed island' is the wordplay.
'destroyed' indicates anagramming the letters.
'island' becomes 'i'.
'enemy' anagrammed gives 'yemen'.
'yemen'+'i'='YEMENI'
(Other definitions for yemeni that I've seen before include "Arab national" , "Native of a country on the Arabian Peninsula" , "Native of Sana'a, say" , "Inhabitant of the country at the southern end of the Arabia" , "Person from Sana'a, say" .)