Crown document:
This is a very specific intel analyst term which "means this is the central document that proves everything else and everything else leads to it. It's the nexus of the information out there that we're putting forward." The document is a critical piece otherwise all the other details fall apart.
Crown document = First Steele Memo?
(or the dossier in general)
June 20, 2016: Steele writes first memo of the dossier. It alleges that Trump used prostitutes during a visit to Moscow in 2013 and that the Kremlin was blackmailing him with the evidence. The memo also alleges that the Trump campaign was engaged in a well-orchestrated collusion campaign with Russian operatives.
Timeline
https://dailycaller.com/2017/10/28/finally-a-definitive-timeline-showing-when-clinton-dnc-started-the-russian-dossier/