var circle = new Circle({
center: evt.mapPoint,
geodesic: true,
radius: 0.0568182, // 300 feet
radiusUnit: "esriMiles"
});
if you create a circle like this or any other fashion in JSAPI 4.6, It appears as if the circle object has an undefined extent unlike in JSAPI 3.x where circle.getExtent() would return a proper Extent type object.

Still new to 4.x. Happy to get advice on what i might be doing wrong. Any body else who can confirm - it is greatly appreciated.