Although Clean is my fave and I would love for that song to be performed, she cannot sing it for anything live
Enchanted/Wildest Dreams, although not likely, would be the best option. It's a nice ballad that turns into a stadium anthem and that's the kind of energy an opener needs. Also, WD has had a lot of longevity and it's very well loved by the GP.
She probably sounds just as bad in New Romantics as she does Clean and the GP will probably think it a basic bop cause they don't really know the lyrics so it'll go over their heads.