\setcounter{errorcontextlines}{999}
\documentclass[twoside]{article}
\usepackage{showframe,lipsum}
\usepackage[innermargin=-2.0cm,]{fullwidth}
\begin{document}
\lipsum

%\clearpage
\begin{fullwidth}[width=\linewidth+2cm]
Start\par
\lipsum[1] \lipsum \lipsum
ENDE
\end{fullwidth}
\end{document}