Enemy tortured one Arab (6)
I believe the answer is:
yemeni
'arab' is the definition.
(I know that Yemeni is a type of arab)
'enemy tortured one' is the wordplay.
'tortured' indicates an anagram.
'one' becomes 'i' (Roman numeral).
'enemy' with letters rearranged gives 'yemen'.
'yemen'+'i'='YEMENI'
(Other definitions for yemeni that I've seen before include "Native of Sana'a, say" , "Someone from Aden?" , "Inhabitant of the country at the southern end of the Arabia" , "Eg, native of Sana'a" , "Arab national" .)