Roman date (4)
I believe the answer is:
ides
'roman date' is the definition.
(Roman calendar term, as in the Ides of March)
This is the entire clue.
(Other definitions for ides that I've seen before include "Orfes" , "Period in month" , "Mid-month date in Roman calendar" , "Eg March 15" , "Unlucky day for Julius Caesar" .)