Clue: Bavarian king ran from Walpole's castle (4)
Answer: OTTO
Explanation: Bavarian king ran from Walpole's castle (4)
[RAN *from*]** OT**(ran)**TO **("Walpole's castle") 
*The Castle of Otranto (published in 1764), regarded by many as the first gothic novel, was written by Horace Walpole, and Otto was King of Bavaria from 1886 to 1916, although due to his limited mental abilities, Bavaria was actually ruled by regents in his stead.