Most races supported by posh hotel where runners abound (2,6)

I believe the answer is:

st moritz

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

'where runners abound' is the definition.
The definition suggests a singular noun which matches the answer.

'most races supported by posh hotel' is the wordplay.
I cannot quite understand how this works, but
an anagram of 'most' is 'stmo' which is located in the answer.
'hotel' could be 'ritz' (I've seen this before) and 'ritz' is located in the answer.
This accounts for all the letters.
This explanation may well be incorrect...

Can you help me to learn more?

I've seen this clue in The Telegraph.

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