Brilliant money (7)

I believe the answer is:

capital

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'brilliant money' is the definition.
'capital' can be an answer for 'money' (I've seen this before). I'm not sure about the 'brilliant' bit.

'brilliant money' is the wordplay.
'brilliant' becomes 'capita' (I can't explain this - if you can you should give a lot more credence to this answer).
'money' becomes 'l' (L can mean 'pounds').
'capita'+'l'='CAPITAL'

Can you help me to learn more?

(Other definitions for capital that I've seen before include "Principal city" , "Upper-case letter" , "Seed money" , "Fantastic!" , "Upper case city" .)

I've seen this clue in The Telegraph.

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