### Clue: Ancient chief shut up, having become tedious (9)
### Answer: PENDRAGON 
 ### Explanation: Definition: Ancient chief
 PEN(to shut up, eg. livestock in an enclosure) **plus**(having) DRAG ON(to become tedious).
Answer: From the Welsh "head or chief dragon", the name of several traditional kings of the Britons, most famous of which was Arthur, he with the Round Table of knights.