Country south of Saudi Arabia (5)
I believe the answer is:
yemen
'country south of saudi arabia' 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" , "Arabian republic, capital Sanaa" , "nation" , "Country between the Red Sea and the Gulf of Aden" , "Republic sited on the SW corner of Arabia" .)