Tired king wearing busby inside out (6)
I believe the answer is:
bleary
'tired' is the definition.
('bleary' can be similar in meaning to 'tired')
'king wearing busby inside out' is the wordplay.
'king' becomes 'lear' (I've seen this before).
'wearing' means one lot of letters goes inside another.
'inside out' suggests removing the centre (throwing the inside away).
'busby' with its centre removed is 'by'.
'lear' going inside 'by' is 'BLEARY'.
(Other definitions for bleary that I've seen before include "Smudged, indistinct" , "Tired and unfocused" , "with tired eyes" , "Like the unfocused vision" , "Unable to see properly" .)