Ageless, in poesy (6)
I believe the answer is:
eterne
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">ageless in poesy</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for eterne that I've seen before include "everlasting" , "Unchangeable" .)