I will call out hazards at road crossings, such as "Car Right" or "Car Left." I will not add potential confusion by calling out "Clear."
In a high noise situation, “Clear” and “Car” can easily be confused. The consequences of someone acting on what they think is “Clear” when it is in fact a call of “Car” are obvious. When you make a call at an intersection, it should be to notify other riders of a hazard they must react to. Anything else adds unnecessary confusion.
See also Communication in the Pace Line.