Hi @FHan , welcome to the forum. By Speak do you mean the Say extension?
That is built-in but is is an older TTS engine. I don’t know if there is a way for PopClip to directly trigger the newer TTS engine (please let me know if anyone knows a way).
However, you could create your own macOS Shortcut for speaking, and trigger that from PopClip. Here is how to do it: How to run a macOS Shortcut from PopClip