\linewidth plus \cline plus centering using tabularx does not work out

I am trying to create a table using tabularx to stretch a table to over the full page width. Usually, it would not need the full width but I like it better if it's like this. In my table, I have some multirow cells, therefore I use \cline{2-9} instead of \hline at some points. Finally, I would like to have the content of my cells centered. However, I seem to be unable to combine all these aspects.

If I use \begin{tabularx}{\textwidth}{llXXXXXXX} %\textwidth or \linewith leads to the same result stretching works but centering of the cell values does not as can be seen in this example

If I try \begin{tabularx}{\textwidth}{llccccccc} centering works but the something is off with the \cline's and \hline's

Condensed code:

\begin{table}[H]    \centering\begin{threeparttable} %because I'm using footnotes\caption{some caption}\label{tab:some table}\begin{tabularx}{\textwidth}{llccccccc}\toprule&    &\multicolumn{7}{c}{some ID} \\&    &1   &2   &3   &4  &5   &6   &7   \\ \midrule\multirow{2}{*}{This is} &a test &$\sim$   &2   &+&+&+&+&+   \\ \cline{2-9}&not a test    &+&10   &+&+&+&+&--   \\ \hline\end{tabularx}\end{threeparttable}\end{table}

Can anybody help me fix this? This would be great!

PS: I posted this question also on reddit but haven't received an answer yet. If a working solution is found there, I'll let you know.