Yes, but it's not advised. The clock speed is controlled by the OS and the processor itself due to a number of factors, including processor load, temperature, and power availability.
If you reduce the battery to 10-20%, disconnect any external power source, and heat the laptop up to its maximum operating temperature, 95F (35C), it will certainly enter a lower power state, including reducing the processor clock significantly. A small heating pad, such as those used for back pain, below the laptop may be sufficient, and during the winter may be very comfortable for you.
However, it would be better to use the correct tools for performance tuning. Yes, you can simulate your old environment and thereby use your own internal clock, however the software you're using has clocks, timers, and other tools to understand the performance of your work. Given that you may likely upgrade again in several years, or you may use different computers and computing platforms in the intervening time, using crutches like emulators isn't a good long-term solution.
I suggest you instead make use of the built in tools. Regular use will allow you to use them without too much additional effort, so that you can integrate them into your software on the fly.