How would Fireworks know how you wanted it cropped? You'd have to tell it by dragging guide lines or a shape over the image. In that case, it's easier to just to draw the crop lines with the crop tool and double click on it.
By default there's no hotkey for that feature, but you can edit hotkeys by Edit > Keyboard Shortcuts.
It'll prompt you to save a new set (this is normal; it avoids losing the default setup in case you want to revert later), and then the real trick will be finding a key combination that's not already in use.