Ruler favouring the Tories crows, stifling unknown protest forcefully (3,4,6)
I believe the answer is:
cry blue murder
'stifling unknown protest forcefully' is the definition.
I don't know anything about this answer so I cannot tell whether this works.
'ruler favouring the tories crows' is the wordplay.
'ruler' becomes 'CR' (short for Carolus Rex ie King Charles).
'favouring the tories' becomes 'yblue' (I can't explain this - if you can you should believe this answer much more).
'crows' becomes 'murder' (I've seen this before).
'cr'+'yblue'+'murder'='CRY BLUE MURDER'
Can you help me to learn more?
(Other definitions for cry blue murder that I've seen before include "complain very loudly" , "Raise Cain" , "Scream loudly" .)