Astute CIA and USA go off the rails with introduction of spies (9)

I believe the answer is:

sagacious

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'astute' is the definition.
(I've seen this before)

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

(Other definitions for sagacious that I've seen before include "Astute" , "Wise" .)

I've seen this clue in The Times.

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