\documentclass[a4paper]{scrreprt}
\newcommand{\cmd}{\begingroup
  \catcode`_=12 \cmdint}
\newcommand{\cmdint}[1]{%
  \texttt{#1}%
  \endgroup
}

\newenvironment{wrap}{}{}
\usepackage{environ}
\NewEnviron{wrap2}{\BODY}

\begin{document}
\cmd{some_test}

\begin{wrap}
  \cmd{some_test}
\end{wrap}

\begin{wrap2}
  \cmd{some_test}
\end{wrap2}
\end{document}