Yes, you can absolutely hire a magician for just one hour, it is very common to hire a magician for an hour for a drinks reception, small dinner party or birthday party. However the cost to hire a Magician for one hour on a Saturday is going to more than a mid-week booking as magicians are usually booked up for larger events like weddings and corporate events on a Saturday whereas a shorter booking of an hour is much easier and cheaper in the week.
Magician - Roger Lapin
Magician for Weddings, Parties & Corporate Events