Historic Royal book featured in urgent announcement (6)
I believe the answer is:
albert
'urgent announcement' is the definition.
The definition suggests a singular noun which matches the answer.
'historic royal book featured in' is the wordplay.
'historic royal' becomes 'alert' (I am not sure about this - if you are sure you should believe this answer much more).
'book' becomes 'b' (abbreviation for book).
'featured in' indicates putting letters inside.
'alert' going around 'b' is 'ALBERT'.
Can you help me to learn more?
(Other definitions for albert that I've seen before include "Queen Victoria's Prince Consort" , "Kind of watch chain" , "London bridge, Memorial" , "watch may depend on it" , "Einstein or Schweitzer?" .)