Tragic king (4)
I believe the answer is:
lear
'tragic king' is the definition.
(Shakespeare's King Lear)
This is all the clue.
(Other definitions for lear that I've seen before include "Playful king and writer of nonsense verse" , "Shakespear's king" , "The Bard's foolish king" , "Edward, writer of nonsense verse" , "See 27 Across" .)