Dim British king (5)
I believe the answer is:
blear
'dim' is the definition.
(I've seen this in another clue)
'british king' is the wordplay.
'british' becomes 'b' (abbreviation e.g. in BBC).
'king' becomes 'lear' (King Lear).
'b'+'lear'='BLEAR'
(Other definitions for blear that I've seen before include "Blur" , "Make (the eyes) dim" , "Baler (anag.)" , "Watery, blurred" , "Indistinct" .)