The name the number goes by (4,5)

'the' is the definition.
I don't know anything about this answer so I cannot tell whether this works.

'name the number goes by' is the wordplay.
'name' becomes 'title' (eg the name of a book).
'the number goes' becomes 'song' (I can't justify this - if you can you should give a lot more credence to this answer).
'by' says to put letters next to each other.
'title' put after 'song' is 'SONG TITLE'.

Can you help me to learn more?