What is your definition of Priest/Priestess?
What functions do they serve?
What are the expectations or criteria for a Priest/Priestess according to your faith or beliefs?
If a Priest or Priestess is dedicated to a certian God or Goddess, how would their fuction/expectations differ?
A priest is a servant in the house of the god. They attend to the god's material and ritual needs, and have responsibility to maintain the house in good order.
Clergy is a broader term; I think to get there one has to step out of a reconstructionist mindset, because the whole 'ministering to the populace' thing doesn't have a lot attested in ancient references.