Language of ancient Rome (5)
I believe the answer is:
latin
'language of ancient rome' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for latin that I've seen before include "Language of old Romans" , "foreign language" , "Language of old 8 down" , "The language of old Rome" , "and 15 Down: Student area of Paris" .)