One circuit round and round in horse race (5)

'horse race' is the definition.
I know nothing about this answer so I can't judge whether this works.

'one circuit round and round' is the wordplay.
'one' becomes 'i' (Roman numeral).
'circuit' becomes 'lap' (synonyms).
'round' says the letters should be written in reverse.
'and' is a charade indicator (letters next to each other).
'round' becomes 'o' (o is a circular letter).
'i'+'lap'='ilap'
'ilap' backwards is 'pali'.
'pali'+'o'='PALIO'

'in' acts as a link.

Can you help me to learn more?