Obvious about Shakespearean king (5)
I believe the answer is:
clear
'obvious' is the definition.
(similar in meaning)
'about shakespearean king' is the wordplay.
'about' becomes 'c' (circa).
'shakespearean king' becomes 'lear' (King Lear).
'c'+'lear'='CLEAR'
(Other definitions for clear that I've seen before include "Bold" , "Easily understood" , "Set free of charges" , "Evident" , "Plain; unblock" .)