Many a Yemeni (4)
I believe the answer is:
arab
'many a yemeni' 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 "Someone from the Middle East or North Africa, perhaps" , "One from the Middle East or North Africa" , "Small riding horse" , "Native of North Africa" , "Horse of a breed originating in the Middle East" .)