Combining a drop-down with autocomplete and search

This is where a proper label helps. In your example, you have no labels above to indicate what you're asking the user to select.

You're correct in that this is a common UI control. You have a couple of abilities and indicators you can add here; allowing a 'clear' function, and proper labeling.

You don't need the additional 'please select' instructions inside the dropdown. If it's a complex instruction or reason, you can make the label clearer, or even add 'hint text' below the dropdown, so users can have some clarity.