Field docent

From Memory Alpha, the free Star Trek reference

A field docent is a joined Trill who serves as a guide and evaluator for prospective Trill hosts for a symbiont.

Field docents report to the Symbiosis Commission and make recommendations regarding their assigned initiates. A negative evaluation from a field docent almost always means an initiate is removed from the program, their hopes of becoming joined ended.

Curzon Dax served as field docent to Jadzia Dax prior to her joining. Jadzia herself later served as Arjin's field docent, though she was determined not to be as hard on him as Curzon had been on her. Arjin himself was unsettled at being Dax's initiate as the symbiont had a reputation for failing more initiates than any other. (DS9: "Playing God")