Prefix with classical (3)
I believe the answer is:
neo
'prefix with classical' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for neo that I've seen before include "language" , "Prefix donating new" , "Prefix meaning new, maybe one" , "Prefix meaning new or recent" , "Prefix meaning new of modern form of" .)