Cicero's tongue (5)
I believe the answer is:
latin
'cicero's tongue' 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 "and 15 Down: Student area of Paris" , "The language of old Rome" , "demanding subject" , "foreign language" , "Virgil's tongue" .)