Without enquiry or reply, it's squarer to be more certain (5)

I believe the answer is:

surer

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'more certain' is the definition.
('sure' can be a synonym of 'certain')

I cannot understand how the remainder of the clue works.

(Other definitions for surer that I've seen before include "faster" , "More certain and positive" , "more right?" .)

I've seen this clue in the Sydney Morning Herald.

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