How to extract a line from a memo object?

SnookyT <[email protected]> Sun, 4 Sep 2022 11:37:01 -0500
Newsgroups alt.comp.lang.borland-delphi
Organization Aioe.org NNTP Server
Message-ID <[email protected]>
I have used the following line ok
    edtProp.Text := memo1.Lines[8];
but how do I get the line that was clicked on instead of using 8?
thx S