A jester was a type of clown.
Death's Head unwittingly discovered the Seventh Doctor portraying a jester in a Brighton pantomime, but the Time Lord was able to get off stage before the robot mercenary could find him. (COMIC: Time Bomb!)
In 2009 Elijah Spellman told Sarah Jane Smith that mankind had always needed someone to make them laugh, slave or king. In Great Britain they had fools like the harlequin and, in the Middle Ages the jester. (PROSE: Day of the Clown)