It might be traditional filling for pizza just returned (4)

I believe the answer is:

jazz

I'm a little stuck... Click here to teach me more about this clue!

'it might be traditional filling for pizza just returned' is the definition.
The definition suggests a singular noun which matches the answer.

This is all the clue.

Can you help me to learn more?

(Other definitions for jazz that I've seen before include "Music with improvisation" , "Miles Davis music" , "Form of music" , "Cat's music?" , "Music of African-American origin" .)

I've seen this clue in The Sun.

Want a hint initially instead of a full solution? Install my app