Poem changes with lyre user (8)
I believe the answer is:
employer
'user' is the definition.
(I've seen this in another clue)
'poem changes with lyre' is the wordplay.
'changes with' indicates anagramming the letters.
'poem' anagrammed with 'lyre' makes 'EMPLOYER'.
(Other definitions for employer that I've seen before include "One hires staff" , "User; boss" , "One who engages workers" , "Boss or proprietor" , "One paying staff" .)