"A slip of the tongue" - something said in error, usually unintentional
"only a mother could give a child" - A mother's admonitory glance, telling her child that it is being silly.
"reserved chuckle" - The Queen very quietly laughed.
"White-tie State dinner" - a full blown banquet, with the men dressed in full dress uniform or in tailcoats and white ties, and the women in full evening dress.
"showcase" - show off (like a display case in a shop)