In The Shakespeare Stealer by Gary Blackwood, why is Chris Beeston's reference to Leicester important?

The answer depends upon how deeply you want to go with your question.

Beeston's reference is a quick one, but is important because Beeston, who became a very famous and successful Elizabethan actor, was under the patronage of the Earl of Leicester. Any reference to Chris's literal "bread and butter" would have made him prick his ears, since Leicester's troupe was in competition with Shakespeare's King's Men. In the end, Beeston also worked for and managed Shakespeare's players as well, but competition and underhandedness between competing troupes was rampant--not to mention competition for currying the favor of the queen and her most noble courtiers, of whom the Earl of Leicester was one.

Next, it is interesting to note that later in his life, Beeston reveals himself as Simon de Montfort, son of the Earl of Leicester'. Not only is Leicester his patron, he is also his father.

Finally, note that the action surrounding Chris Beeston's reference takes place in Leicester, the only Hub between Stratford-Upon Avon, where Shakespeare was writing, and London, where the excitement, glamour and seediness of an actor's existence is fulfilled. The location represents a metaphorical turning point in the plot as Widget meets Bass and his destiny is driven forward.