Word seen twice on the UN roster (4)
I believe the answer is:
arab
'word seen twice on the un roster' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for arab that I've seen before include "Semite" , "Someone from the Middle East or North Africa, perhaps" , "Horse of a breed originating in the Middle East" , "Qatari or Omani, say" , "Saudi or Omani, perhaps" .)