Top, champion board rider? (7)

I believe the answer is:

surface

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'top champion board rider?' is the definition.
'surface' can be an answer for 'top' (I've seen this before). I am unsure of the 'champion board rider?' bit.

'top champion' is the wordplay.
'top' becomes 'surf' (I can't explain this - if you can you should give a lot more credence to this answer).
'champion' becomes 'ace' (both can mean a person excelling at something).
'surf'+'ace'='SURFACE'

Can you help me to learn more?

(Other definitions for surface that I've seen before include "Top spot" , "Come up for air" , "Superficial appearance" , "Outer appearance" , "Facade" .)

I've seen this clue in The Times.

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