Salt content to find nonuples in half of Brisbane (9)

'salt content' is the definition.
'brininess' can be an answer for 'salt' (thesaurus). I am unsure of the 'content' bit.

'nonuples in half of brisbane' is the wordplay.
'nonuples' becomes 'nines' (I can't explain this - if you can you should give a lot more credence to this answer).
'in' means one lot of letters goes inside another.
'half of' means to take half the letters.
'brisbane' cut in half is 'bris'.
'nines' placed inside 'bris' is 'BRININESS'.

'to find' is the link.

Can you help me to learn more?