Actually, I think it is both. It is a breakout in the sense that against the Vikings he established a new level of play. He played well in the first 4 games, but against the Vikings he was clearly the best Texans lineman on the field.
In the first 4 games Clowney’s stat line was pretty ordinary, but his “game” exceeded his stats. He was solid against the run, set the edge, held his position at the point of attack and chased down plays. Inconsistently, but not infrequently, he pressured the quarterback. Jadeveon did his job by executing the fundamentals that often create stats for others.