A leadin or lead-in is the first clue of a tossup. Per the rules of pyramidality, it is the most difficult clue to buzz off of in a tossup. Leadins must abide by all of the rules for good clues, and when writing leadins, writers should take especial care to avoid stock clues and vague clues.
Leadins often contain information that is more tangentially related to the subject at hand. Examples include literary criticism, opinions of historians, or literature about works of art.
Pop culture in leadins
Though tangential academic information is generally acceptable in leadins to academic tossups, pop culture clues should never be used for leadins.
The term "leadin" can sometimes also refer to the introduction to a bonus, before the first part proper. ("Intro(duction)" is preferred to avoid ambiguity.) Bonus introductions typically identify the theme of the bonus or state an interesting or little-known fact about the first answer. In an oft-criticized practice, some writers insert (usually terrible) jokes or other funn content into their bonus leadins.