Midmonth date (4)
I believe the answer is:
ides
'midmonth date' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ides that I've seen before include "Julius Caesar was told to beware the . . . . of March" , "March 15; dies (anag.)" , "(In March) Caesar's time to beware" , "Caesar's fateful day" , "Caesar's bad day in March" .)