New string on tops of heavily fortified places (12)

I believe the answer is:

strongpoints

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'heavily fortified places' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.

'new string on tops' is the wordplay.
'new' indicates anagramming the letters.
'string'+'on'+'tops'='stringontops'
'stringontops' anagrammed gives 'STRONGPOINTS'.

'of' acts as a link.

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I've seen this clue in The Globe and Mail.

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