Excerpt using Read More Tag

You just need to set the first argument of the_content() to an empty string:

<?php the_content( '' ); ?>

If you don’t pass an argument it will use the default, which is a link with the text “(more…)”, but by passing an empty string, the empty string (i.e. nothing) gets displayed instead.

If you want it in a variable, use get_the_content( '' ) in the same way, but for formatting to match properly you’ll need to apply the the_content filter:

$excerpt = apply_filters( 'the_content', get_the_content( '' ) );