答案1
也许这就是你的目标:
\documentclass{article}
\usepackage{tabularx}
\usepackage[nopar]{lipsum} % for dummy contents
\newenvironment{environment}[1]
{\center\tabularx{\columnwidth}{@{}l|X@{}} #1 &}
{\endtabularx\endcenter}
\begin{document}
\lipsum[2]
\begin{environment}{Something}
\lipsum[3]
\end{environment}
\lipsum[4]
\end{document}