When turning on a motorcycle, you do not necessarily need to use the clutch. Whether or not you use the clutch while turning depends on the specific situation and your riding style.
In general, if you are riding at a low speed or coming to a complete stop before turning, it is common to disengage the clutch by pulling the lever in order to prevent stalling the engine. By doing so, you can keep the engine running while controlling the motorcycle with the throttle, brakes, and clutch.
You can maintain your speed and smoothly roll off the throttle while leaning into the turn. During this process, you may downshift gears to match your speed and maintain optimal engine RPM for the turn, but this can be done without using the clutch.
Using the clutch during a turn can be useful in specific situations, such as when you need to quickly reduce speed or if you encounter a tight, slow-speed turn where additional control is necessary. In such cases, you can pull the clutch lever to disengage the engine power from the rear wheel and control your speed using the brakes and throttle.
Ultimately, the decision to use the clutch while turning on a motorcycle depends on the specific circumstances, your riding style, and your comfort level with different techniques. It's important to practice and develop your skills to determine what works best for you in various riding scenarios.