Lewis & Short

instĭtor, ōris, m. [insisto],

  1. I. a person who sells goods for another, a factor, broker, agent; a huckster, hawker, peddler (cf.: circulator, negotiator): amata nautis multum et institoribus, Hor. Epod. 17, 20: mercis, Liv. 22, 25: hibernae tegetis, Juv. 7, 221.
  2. II. Trop.: eloquentiae, who hawks about his eloquence, makes an exhibition of it, Quint. 11, 1, 50; id. 8, 3, 12.