Control click on each way you want to remove from the selection, maybe? (Assumes you selected members from the relation list rather than the relations themselves.)
Edit: I realise this is probably only 5 ways in your example. If you'd selected instead all the relations to get the outermost polygon then deselecting as I suggest would be worse than just selecting the ones you want to include. I suspect you're after something else again.again.
Another edit: You could try zooming to a visible window completely inside the outer polygon you wish to leave selected, and Search, Remove from Selection, Inview