About, before a year (5)
I believe the answer is:
circa
'about before a year' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for circa that I've seen before include "Roughly" , "Approximately, around" , "(Especially of a date) approximately" , "Approximately (of a year)" , "Preposition meaning about, usually preceding a date" .)