Classic appearing in 151 AD (5)
I believe the answer is:
iliad
'classic' is the definition.
(I've seen this before)
'151 ad' is the wordplay.
I cannot really understand how this works, but
'ad' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
'appearing in' is the link.
Can you help me to learn more?
(Other definitions for iliad that I've seen before include "No short tale" , "Work on war" , "set of books" , "ancient tale" , "Old story" .)