Clover is always a good choice to plant with anything, but you might also consider and annual grain that will not shade out the radishes. Oats or winter wheat might be a good choice. I find it best to give deer a variety of choices when creating a food plot.
Radishes would be considered a brassica similar to turnips and one of the things that will make a brassica attractive to dear is that after it turns cold and your have frost the leaves will create more sugar making the plant more palatable. So planting radishes in the spring probably not attract deer as much as planting them in the fall.
“There are two spiritual dangers in not owning a farm. One is the danger of supposing that breakfast comes from the grocery, and the other that heat comes from the furnace.”