Dim British king on stage (5)
I believe the answer is:
blear
'dim' is the definition.
(I've seen this before)
'british king on stage' is the wordplay.
I cannot really see how this works, but
'british' could be 'b' (abbreviation e.g. in BBC) and 'b' is found within the answer.
'king' could be 'lear' (Shakespeare's King Lear) and 'lear' is located in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for blear that I've seen before include "Indistinct" , "Make (the eyes) dim" , "Blur" , "Baler (anag.)" , "Watery, blurred" .)