Most in French resort upset during holiday? One should minimise health risk (11)

I believe the answer is:

vaccination

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'one should minimise health risk' is the definition.
(a vaccination reduces risk from an illness)

'most in french resort upset during holiday?' is the wordplay.
'most in french resort upset' becomes 'cin' (I can't justify this - if you can you should believe this answer much more).
'during' indicates putting letters inside.
'holiday?' becomes 'vacation' ('vacation' can be a synonym of 'holiday').
'cin' inserted into 'vacation' is 'VACCINATION'.

Can you help me to learn more?

(Another definition for vaccination that I've seen is " Immunising treatment".)

I've seen this clue in The Guardian.

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