The term that refers to the clustering of sensory structures at the anterior end of an organism is cephalization.

Here's why:

* Cephalization is the evolutionary process where sensory organs and nerve tissues become concentrated at the front end of an animal, forming a head. This allows for better sensing of the environment and more efficient response to stimuli.

* Anterior refers to the front or head end of an organism.

Therefore, cephalization describes the concentration of sensory structures at the anterior (head) end of an organism.