Tragic king stops by, dull with sleep (6)
I believe the answer is:
bleary
'dull with sleep' is the definition.
(I've seen this before)
'tragic king stops by' is the wordplay.
'tragic king' becomes 'Lear' (Shakespeare's King Lear).
'stops' means one lot of letters goes inside another (stopping can mean blocking a gap).
'lear' going into 'by' is 'BLEARY'.
(Other definitions for bleary that I've seen before include "(Of eyes) dull and un-focussed from sleep" , "Blurred" , "Eyes like this are dull from exhaustion" , "Dim" , "Unable to see properly" .)