Swiss areas preserve huge amounts (7)

I believe the answer is:

cantons

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'swiss areas' is the definition.
'Cantons' can be an answer for 'areas' (Canton is an example). I'm not sure about the 'swiss' bit.

'preserve huge amounts' is the wordplay.
'preserve' becomes 'can' (canning is a kind of preserving).
'huge amounts' becomes 'tons' (ton is a kind of amount. I am not sure about the 'huge' bit.).
'can'+'tons'='CANTONS'

Can you help me to learn more?

(Other definitions for cantons that I've seen before include "Swiss administrative divisions" , "Territories" .)

I've seen this clue in The Times.

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