Think twice about anaesthetist knocking out ants (8)

I believe the answer is:

hesitate

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

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

(Other definitions for hesitate that I've seen before include "Delay making a decision" , "Vacillate" , "Stall" , "Lack confidence" , "Dither indecisively" .)

I've seen this clue in The Irish Times.

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