It's possible that:
* The name is misspelled. Could you double-check the spelling?
* The person works in a different area of entertainment (e.g., behind-the-scenes) and is not widely known.
* The person is relatively unknown. It's possible that Mark Clem is a budding actor or filmmaker with limited projects.
To help me find the information you're looking for, could you provide more details? For example:
* What type of projects are you interested in? (Movies, TV shows, documentaries, etc.)
* What is the person's role? (Actor, director, writer, etc.)
* Do you know any additional details about the person or their work? (Where they are from, any specific genres they work in, etc.)
With more information, I can hopefully assist you in finding what you're looking for.