Putting the king under threat but holding back (8)

I believe the answer is:

checking

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'holding back' is the definition.
('check' can be a synonym of 'hold back')

I don't understand the rest of the clue.

(Other definitions for checking that I've seen before include "Verifying" , "Ecamining for accuracy, quality, or condition" , "Establishing that something is correct" , "Inspecting for accuracy" .)

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

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