Nigel Farage is the incumbent Member of Parliament for Clacton and the de-facto leader of Reform UK, a populist right-wing party that has only a handful of MPs but is currently leading the polls. He is being investigated by the Parliamentary Standards Committee over personal donations he accepted prior to becoming an MP. In response to this investigation, Farage stood down as MP, triggering a by-election (a special election held when an MP resigns, dies or is otherwise removed from their seat mid-term).

Farage announced his intention to stand in this by-election (which he is entitled to do), arguing that only his constituents had the right to decide whether he was fit to be a Member of Parliament. He argues that the Standards Committee is fundamentally illegitimate because he would be judged by his political rivals; in any case, the greatest sanction the committee could impose would be his expulsion from parliament, which would trigger a by-election that he would be entitled to stand in. The other major parties have all decided not to stand candidates against Farage in the Clacton by-election, creating this slightly farcical contest between the incumbent and a joke candidate.

Thanks for the explanation!