Not a dry subject but dictators shy from it (12)

I believe the answer is:

hydrostatics

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'it' is the definition.
The definition suggests a singular noun which matches the answer.

'not a dry subject but dictators shy' is the wordplay.
'dictators shy' anagrams to 'HYDROSTATICS'.
However, I'm not clear how the anagram is indicated.

'from' is the link.

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

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