Mounted nothing in this competition (5)

I believe the answer is:

rodeo

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

'mounted nothing' is the wordplay.
'mounted' becomes 'rode' (I can't explain this - if you can you should believe this answer much more).
'nothing' becomes 'O' (O resembles 0).
'rode'+'o'='RODEO'

'in' acts as a link.

Can you help me to learn more?

(Other definitions for rodeo that I've seen before include "A bunch of cowboys, showing" , "show with mounting excitement" , "Mounted exhibition" , "skilful exhibition?" , "One should be up for this event" .)

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

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