About function; money returned for horseman (9)

I believe the answer is:

caballero

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

'for horseman' is the definition.
(I've seen this before)

'about function money returned' is the wordplay.
'about' becomes 'ca' (short for circa).
'function' becomes 'ball' (ball can mean a party or function).
'money returned' becomes 'ero' (I can't explain this - if you can you should believe this answer much more).
'ca'+'ball'+'ero'='CABALLERO'

Can you help me to learn more?

(Other definitions for caballero that I've seen before include "Spanish gent" , "Spaniard politely" , "Horseman" , "Spanish gentleman" , "Cowboy" .)

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

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