Body’s flanks okay for operation (6)

I believe the answer is:

bypass

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

I don't understand the remainder of the clue.

(Other definitions for bypass that I've seen before include "Go round (congested area etc)" , "Road built to avoid a congested area" , "Round-about way" , "Road built to avoid another" , "Way to avoid town etc" .)

I've seen this clue in the Sydney Morning Herald.

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