Das Böse ist manchmal in der Hand wie ein Werkzeug, erkannt oder unerkannt läßt es sich, wenn man den Willen hat, ohne Widerspruch zur Seite legen.
Evil is sometimes like an instrument in the hand; recognized or unrecognized, it lets itself be laid aside without protest if one so wills. [Kaiser/Wilkins]
Evil is sometimes like a tool in your hand; recognized or unrecognized, you are able, if you have the will to do it, to set it aside, without being opposed. [Hofmann]
If it's your will, who could oppose you?
What is being laid aside? The desire to harm others, selfishness, indifference, or some other motive or psychological state? Or is it an action, or a state of affairs? Kafka might be pointing to the moment of decision, when one really renounces something; then, there is no struggle, the act is simple and easy. Where there is a struggle against evil, there is evil. Evil is not separable from the struggle against Evil. I'm not sure that Kafka would say that the absence of struggle necessarily means the absence of Evil, though.
Perhaps contracting the circle involves not straying from the vigilance, which is not only about keeping watch, but about making sure that what there is to keep watch over doesn't become so ungainly, oversized, complicated, murky, that you can't see it. I think Kafka was intrigued by things, particularly man-made things, like the Law, which become so vast that no one person can know them anymore. Individual specialists may know a corner very well, but no one can know what all those corners add up to. So contracting the circle is mainly, I would say, about not losing track.