The —, Greek epic poem describing the siege of Troy (5)
I believe the answer is:
iliad
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">the greek epic poem describing the siege of troy</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for iliad that I've seen before include "Homer's tale" , "Homer's great poem" , "A work by 7" , "long story" , "Epic piece of writing" .)