Satellite city to knock back radium affair by the sound of it (10)

'affair by the sound of it' is the definition.
I can't tell whether this defines the answer.

'satellite city to knock back radium' is the wordplay.
'satellite city' becomes 'matta' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'to' means one lot of letters go next to another (I've seen this in other clues).
'knock' becomes 'rap' (synonyms).
'back' says the letters should be written in reverse.
'radium' becomes 'Ra' (Ra is the chemical symbol for radium).
'rap' in reverse letter order is 'par'.
'par'+'ra'='parra'
'matta' put after 'parra' is 'PARRAMATTA'.

Can you help me to learn more?