Give a rough estimate (5)

I believe the answer is:

guess

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'estimate' is the definition.
(I know that estimate can be written as guess)

I don't understand how the rest of the clue works.

(Other definitions for guess that I've seen before include "Make stab at" , "Imagine" , "Hypothesis" , "Speculate" , "Reckon" .)

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

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