Necessary balance between composer, allowance and music practice (8,6)

I believe the answer is:

bathroom scales

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

'between composer allowance and music practice' is the definition.
I know nothing about this answer so I cannot tell whether this works.

'necessary balance' is the wordplay.
'necessary' becomes 'bathroom' (I can't justify this - if you can you should believe this answer much more).
'balance' becomes 'scales' (balance can mean a set of scales).
'bathroom'+'scales'='BATHROOM SCALES'

Can you help me to learn more?

I've seen this clue in the Sydney Morning Herald.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.