you might be able to do this with the "add mixing transform" action (at least that's how I do it). Define the animation, and the upper most bone in the hierarchy ( like for a clap animation, it might be a spine or chest bone) and set it to recursive. That way you'll still be running while clapping, because everything which isn't in the hierarchy you defined won't be animated by that particular clap animation (but by your walkcycle/idle etc)
Animation layers can be defined in the animation settings action though, if still needed.