Draw an arc with Curves - Center, Point, Angles.
Or cut an existing full circle into pieces with Modify - Divide. And then delete the unwanted part. If you want to define the cutting points by clicking somewhere on the circle (when no exactness needed), be sure to have Snap on Entity enabled.
You may also use Modify - Trim and trim to an other element, but this can be tricky.
There is no tool to automatically delete an element between intersection points with other elements, unfortunately.