Why does it not meet the posted definition? To be a mechanism it simply has to be interacting parts (brain cells etc) causing an effect…information. A mind is clearly a causal mechanism.
Mechanism and process are different things. A process is the cause and effect of several mechanisms. We can represent a process diagram by several boxes where Box A is the cause of Box B and so on. After DNA is available to the cell then several processes are enabled. These processes are understood however the origin of the genetic information in DNA is not. This is where mind is a cause that is known to create the effect of long complex sequences or genetic information.
Einsteins theory of general relativity has causal mechanism as mass/ energy to explain space time curvature. There is some more detail in the stress-energy tensor but it is the same idea.
Joshua suggested in the discussion with Gpuccio to have negative controls. This is a great suggestion and is a way to eliminate other potential causes like random variation.