Dead language (5)
I believe the answer is:
latin
'dead language' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for latin that I've seen before include "Shakespeare's was small, according to Jonson" , "Parent language of French,Romanian" , "Language of Cicero" , "and 15 Down: Student area of Paris" , "Romantic language" .)