Pressure by itself isn't that useful for producing energy, except for the piezoelectric effect. However, you don't get a lot of energy from the piezoelectric systems. To use the pressure to power some sort of generator, you'd need a difference in pressures. That's hard to maintain in a Venus environment. As for temperature, you might be able to directly generate electricity using thermocouples, but the efficiency is very low (typically < 5%).

Since the real killer for a Venus lander is the heat, the hard part is keeping the electronics from frying for long enough to do useful science. Ironically, vacuum tubes are much less sensitive to heat than solid-state electronics but they're a lot bulkier, more vulnerable to vibration, and are just about out of production anywhere. There are some solid state systems that can withstand a fair amount of heat, but most of them begin to die at or below 100 degrees C, a temperature far lower than the surface of Venus.

The Soviets used a clever system of super insulation and cold-soaking the lander before entering the atmosphere, then operating as long as possible before the heat killed it. Designing a refrigeration system to withstand that hellish temperature would probably require a lot of electrical energy, probably a lot more than you could generate with piezoelectric crystals or thermocouples. That's a real problem. Solar cells are probably out of the question because of the cloud cover and temperatures on the surface. Primary cell batteries can operate for a time and would probably be the way to go. They can power a lander from minutes or hours depending on the capacity and current loads.