Do take my advice with a grain of salt. I'm not an expert, just someone who loves lifting and reads too many books. But if it makes sense, it makes sense.
Here's a couple of ideas on a those Sunday Power Cleans. Other than warming up, their purpose is to train explosiveness, yes? In that case, rather than lightening the weight artificially, could finding a lift that's further along the continuum work?
A Power Snatch may serve as well. The greater pulling distance will force you to use a lighter weight, but still demand explosiveness. A One Hand Snatch, DB or better a BB will reduce the weight further.
A One Hand Clean may too. In this case you're still lifting with both legs, and torso, but all the energy passes through one hand. This will have the added benefit of strengthening your grip. I'm not sure what the ratio is, but 70% to 80% of your regular Power Clean would be reasonable.
So again you're doing a lighter pull, this time limited by grip. You can grip the bar overhand, or under. I favour under as it sets me up well for pressing, but the other way can be good too. If you want, after cleaning, you can put your other hand on the bar and get a sneaky eccentric curl as you lower the weight. When doing it, the best lifters place their offhand on their thigh just above the knee and push off with it at the same time as pulling with the other.
Below is a vid showing how I do it underhand, and the following vid is a better example, (but with a jerk).