For 11 23, you need to think of the main murderer of Caesar and what Caesar said about him (a thin fellow!) - the question is whether he would have murdered Caesar if he had been different (not thin - ?B?S?R)
5D - do some research into the lady who is Queen in the Underworld in the springtime only - Demeter was her mother!
4D is a lovely 'heard' clue - look for a foreign word for the masses that sounds like CAN I? - come back to me if those don't help.