It depends on if he is acting as a representative of a higher clergy member. In Roman catholicism it was used when higher clergy were referring to their representatives. Even the pope is called the "Vicarius Christi", meaning vicar (representative) of Jesus Christ. In the Church of England, it could refer to parish priests depending on how they were appointed to the position. If in your story it's just the churchgoers talking to him then I would go with father. If in your story he is working for the archbishop or someone to that effect, the archbishop could refer to him as a vicar. http://www.newadvent.org/cathen/15401a.htm http://en.wikipedia.org/wiki/Vicar
