Where is the crop tool?

[Egg Bramhill]

The crop tool is in the camera tools fly-out.
Your profile doesn't say what Xara product you're using? If it's Xtreme, I don't think it has a crop tool. If so create a rectangle, give it 50% transparency, move it over the photo, resize to required size. Shift select the photo, Arrange / Combine shapes / Intersect shapes.
Edit.Again if it's Xtreme, double clicking the image opens the Picture Editor. I'd completely forgotten that existed