A licence fee is the money paid by the individual Briton for each television in their house. Viewed variously as a tax or a privilege fee, it is a major source of revenue for the production of programming transmitted by the British Broadcasting Corporation. Doctor Who has traditionally depended on this money for its production costs.
The fee is a political football, with members of the Conservative Party generally hoping to lower or even eliminate it, while members of the Labour Party typically argue that it's the main reason BBC programming is of a generally higher quality than that of other networks, such as ITV.
People related to Doctor Who have, somewhat unsurprisingly, voiced their opposition to licence fee cuts. Russell T Davies, for instance, was staunchly opposed to the licence fee freeze David Cameron's government instituted in 2011. Likewise, David Tennant was one of many stars to protest Cameron's licence fee plans prior to moving into Number 10.