Suddenly leaves king protected by rooks (6)
I believe the answer is:
scrams
'suddenly leaves' is the definition.
(I've seen this before)
'king protected by rooks' is the wordplay.
'king' becomes 'R' (abbreviation for rex, king in Latin).
'protected by' indicates putting letters inside (inserted letters are held or protected).
'rooks' becomes 'scams' (I've seen this in another clue).
'r' put into 'scams' is 'SCRAMS'.
(Other definitions for scrams that I've seen before include "Buzzes off, vamooses" , "Suddenly leaves" , "goes off, it's said" .)