[xxpinballxx]

Please answer questions here whenever possible. Simply editting the image and posting is not really a help to anyone looking for the same information.
The questions here are meant to be helpful...for everyone who reads it not just the original poster.

I also say clone it. you'll want to try and complete the cloude or make it look natural and without any repetition in obvious marks. SO in this case I'd grab a spot right on the edge of the white so it includes the white cloud and the sky. then make the brush large enough to cover most of the area neede to cover. The more spots you clone the more chaces you'll see it. There really isnt an easy way to do this...just make sure your history brush is set high enough to step back if you think it looks obvious.
A bit of practice I did was just picking images and try cloning poles or powerlines out of it and then gradually got to cloning all sorts of things.