so some time back I was used as a money mule without realising by someone I trusted very much. Once he had everything he wanted (money) he then blocked me leaving me with a debt of more than £5000. I now have a CIFAS marker and want it removed but where do I start
Your starting point would be to contact CIFAS and do a subject access request.
Whether or not you can have it removed depends on persuading whoever lodged the marker to remove it. If the marker was for being involved in fraud, rather than being a victim of fraud, then you may be stuck with the marker for years to come.