The Collaborative International Dictionary of English v.0.48:
Booking clerk \Book"ing clerk`\ A clerk who registers passengers, baggage, etc., for conveyance, as by railway or steamship, or who sells passage tickets at a booking office. [1913 Webster]WordNet (r) 3.0 (2006):
booking clerk n 1: someone who sells tickets (e.g., theater seats or travel accommodations) [syn: ticket agent, booking clerk]