One making a speech at Number Ten - to music (8)
I believe the answer is:
oratorio
'to music' is the definition.
(oratorio is a kind of music)
'one making a speech at number ten' is the wordplay.
'one making a speech' becomes 'orator' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'at' says to put letters next to each other.
'number ten' becomes 'IO' (IO resembles o0).
'orator'+'io'='ORATORIO'
Can you help me to learn more?
(Other definitions for oratorio that I've seen before include "Composition for voice and orchestra with biblical theme" , "Sacred, dramatic music" , "Religious musical drama, unstaged" , "Large choral work" , "Comprehensive music" .)