Manage to keep cool about the untrue part (7)

I believe the answer is:

control

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But I can't explain it at all! Could you help me understand?

(Other definitions for control that I've seen before include "Regulate with self-possession?" , "Exercise power over" , "Power to restrain or regulate" , "Keep in line" , "Direct or determine" .)

I've seen this clue in the Evening Standard.

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