Epic poem of 151 AD (5)
I believe the answer is:
iliad
'epic poem' is the definition.
(Iliad is an example)
'151 ad' is the wordplay.
I cannot really see how this works, but
'ad' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
'of' is the link.
Can you help me to learn more?
(Other definitions for iliad that I've seen before include "set of books" , "story of Mediterranean heroism" , "literary work" , "Old story" , "Homer's epic poem on the siege of Troy" .)