Wicket

Wicket was a cricketing term with three definitions.

Primarily, it was the object of central focus in the sport of cricket. Comprised of three stumps and two bails, it was the thing that batsmen were guarding and the thing bowlers were attacking. Batsmen were dismissed if the bowler made the bails fall off the stumps by sending his ball past the batsman into the wicket. This act often drew loud reaction by on-lookers and players alike. From inside the comfort of the Black Horse Inn in the village of Cherhill, the Brigadier, for instance, could hear the spectators react when wickets fell. (PROSE: The Shadows of Avalon)

A wicket was also a synonym for the cricket pitch itself, as Lord Charles Cranleigh made clear when he called the wicket on the Cranleigh Hall ground "very green". (TV: Black Orchid) The Fifth Doctor himself also clearly indicated the meaning when on the Eye of Orion with Tegan and Turlough. He suggested that they could all play a few impromptu overs if only they could find a place to mark out the pitch. He found the particular ground he was marking out to be a "bit of a bumpy wicket" as he was pacing out the area to place the stumps. (PROSE: The Eight Doctors)

Finally, it could be a way of keeping score. The MCC, for instance, were said to have "won by four wickets" against All India in the second 1926 test between them.

Behind the scenes
The third definition is not adequately explained in DWU fiction. When used as an apparent score, a wicket is an un-dismissed batsman. So to say that the MCC "won by four wickets" means that of their ten total batsmen, four were "not out" because they'd never even been required to bat once. In other words, the MCC got all runs needed to win with just six batsmen, so the match was won by a sufficiently comfortable margin that the number of runs scored wasn't necessary to convey the magnitude of the victory.