Claret Cup is an iced drink made with claret (red Burgundy) and a range of other ingredients which may include soda water, brandy, sherry, curaçao, maraschino, fruit juices, sugar, cucumber and fruit.
It was a popular drink during Victorian times, and there are two references to it in the Rev. Francis Kilvert's diary* entry for July 12th. 1870, where he notes the following:
A crowd in the drawing room drinking claret cup iced and eating enormous strawberries;
High tea at 7.30 ... More than 40 people sat down. Plenty of iced claret cup, and unlimited fruit ...
Recipe for Claret Cup (Mrs. Beeton 1831).
*The Rev. Francis Kilvert, Kilvert's Diary 1870-1879 (Jonanthan Cape, 1964).