Speaker — one with old composition (8)
I believe the answer is:
oratorio
'composition' is the definition.
(type of musical composition)
'speaker one with old' is the wordplay.
'speaker' becomes 'orator' (orator is a kind of speaker).
'one' becomes 'i' (Roman numeral).
'with' is a charade indicator (letters next to each other).
'old' becomes 'o' (abbreviation).
'orator'+'i'+'o'='ORATORIO'
(Other definitions for oratorio that I've seen before include "Religious musical work" , "Sacred music composition" , "Sung composition based on a religious theme" , "E.g. Messiah or Elijah" , "Large-scale choral work" .)