"The Rubáiyát" poet (4)
I believe the answer is:
omar
'the rubaiyat poet' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for omar that I've seen before include "- Khayyam, Pers. poet" , "- - Sharif (films)" , "Arab" , "and 16 Down: Persian poet" , "- Sharif, film actor" .)