Check mate for Eeyore? (6)

I believe the answer is:

assess

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'check' is the definition.
The answer and definition can be both related to thinking as well as being verbs in their base form.
Maybe you can see an association between them that I don't see?

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for assess that I've seen before include "Evaluate, estimate" , "Estimate the worth or quality of" , "price" , "Estimate value (for tax)" , "Gauge, evaluate" .)

I've seen this clue in The Telegraph.

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