Heard about king rejecting study (7)
I believe the answer is:
learned
'heard about' is the definition.
('learn' can be a synonym of 'hear about')
'king rejecting study' is the wordplay.
'king' becomes 'lear' (Shakespeare's King Lear).
'rejecting' says the letters should be written in reverse.
'study' becomes 'den' (term for a study or office).
'den' in reverse letter order is 'ned'.
'lear'+'ned'='LEARNED'
(Other definitions for learned that I've seen before include "Discovered, ascertained" , "Intellectual" , "Absorbed information about Leander" , "Came to know" , "Studied" .)