Are you using lemonade as in pink lemonade or the like, or are you using a sparkling beverage, like sprite or something like it? In case of the former, I got nothing. In case of the latter (which is what's being done here in German-speaking Europe), I recommend you either brew up a pale ale with subdued hop aroma (preferably C-hops as I imagine they meld well with the lemonade, and there is one commercial Austrian brewery that uses Cascade for their NA-Zwickel which makes a decent Radler) and a neutral ale yeast at low temps. Or you take a more daring approach and brew a relatively lightweight Wit-like concoction using Orange peel and coriander and either a white wine or champagne yeast, which is something I have done in the past. Mixed very well with Fanta or Sprite (traditional soda pop choices for making Radler) or Almdudler (a herb based soda pop not entirely unlike ginger ale). This didn't give me Radler in the conventional sense, but it was a marvellously refreshing beverage for hot summer days and yardwork.