Neighbor of Oman (5)
I believe the answer is:
yemen
'neighbor of oman' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for yemen that I've seen before include "Country bordering Oman" , "Republic sited on the SW corner of Arabia" , "Country between the Red Sea and the Gulf of Aden" , "Republic by the Red Sea" , "nation" .)