Spooner’s dirty concrete getting palace’s approval (5,4)

I believe the answer is:

royal seal

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

'spooner's dirty concrete' is the definition.
I can't judge whether this defines the answer.

'palace's approval' is the wordplay.
'palace's' becomes 'royal' (I can't explain this - if you can you should give a lot more credence to this answer).
'approval' becomes 'seal' (seal is a kind of approval).
'royal'+'seal'='ROYAL SEAL'

'getting' is the link.

Can you help me to learn more?

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

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