Poe poem: name later changed (9)
I believe the answer is:
tamerlane
'poe poem' is the definition.
(Tamerlane is a poem by Edgar Allan Poe)
'name later changed' is the wordplay.
'changed' indicates an anagram.
'name'+'later'='namelater'
'namelater' anagrammed gives 'TAMERLANE'.
(Other definitions for tamerlane that I've seen before include "Mongol who conquered" , "Fighter of legend" , "medieval conqueror" , "He conquered a huge area" .)