Show disapproval of king's title (4)
I believe the answer is:
book
'title' is the definition.
(thesaurus)
'show disapproval of king's' is the wordplay.
'show disapproval of' becomes 'boo'.
'king' becomes 'k' (abbreviation for king in chess).
'boo'+'k'='BOOK'
(Other definitions for book that I've seen before include "Reserve - bets taken on a race" , "thing that shouldn't be cooked?" , "Reserve; tome" , "strict regulations" , "Hardback, say" .)