Some brain-storming (and probing) ideas -
1. As R20190 suggested, watch for his deep clears being out - let one or two of suspicious ones drop, and check to see if he's bluffing.
2. Intentionally feed him somewhat shorter clears/lifts, to entice another clear, and see if he could adapt height/power of his own deep clears to keep them in. If he's other dangerous varieties, this may not work well, but at least worth a try once or twice in order to "understand" him. You may need to do this a few times, to gather/confirm data points.
3. Like everything else, if you find his clears the most troubling, try to deprive him of his option to play those shots. In other word, refrain yourself from playing lifts/clears that enable him to play those clears that bug you.
4. Your own clears might be hit too high (or short already). Check what happens if you flatten your clears, and see if you can cause him problems in getting behind the shuttle and generate enough power. Also check the length of your own clears by taking a peek of where he stands when he takes yours.
If you lose experimenting with your ideas, you can always play another game with changed strategy, right?