The __, epic poem by Homer (5)
I believe the answer is:
iliad
'the epic poem by homer' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for iliad that I've seen before include "Greek epic poem describing the siege of Troy" , "heroic work" , "Work on war" , "Homer's epic poem on the siege of Troy" , "Homer Trojan war epic" .)