Thanks. I sorted this out (with the help of google of course).
For anyone interested this is what you can do:
Before BODY is closed additionalhtmlfooter
Step 2. Enclose the variable portion of your course description like this:
<p>A course to prepare for whatever</p>
<a href="#" onclick="toggle_visibility('foo');">See more. . .</a>
<div id="foo" style='display:none;>
<p>More text than we can comfortably display. . .</p>
<p>Several paragraphs in fact</p>
<p>Mind the div closing tag goes at the end.</p>
And that is all there is to it. Click on 'See more. . .' to display the hidden text and again to hide it.
Of course, this might be the brute force way of doing things. If there is some sort of setting or other builtin way to accomplish this then I would like to know. We are presently using Moodle-2.8.