Note that this becomes quite easy if you use the Sideview Table module instead of the SimpleResultsTable module, and it doesn't require writing a custom module or any custom code at all.
Say your field was called "url", and say it was a fully formed URL, including the http:// and all that. All you would use is the following XML in your view:
<module name="Table">
<module name="HTML" group="row.fields.url">
<param name="html"><![CDATA[
<a href="$row.fields.url$">$row.fields.url$</a>
]]></param>
</module>
</module>
There are docs about this feature within Sideview Utils itself. Note that you'll need a relatively recent version of Sideview Utils (currently 2.3) from the Sideview site ( http://sideviewapps.com/apps/sideview-utils ) and not the older version available on Splunkbase.
Once you get the app installed/upgraded, you can find those docs under "Module Documentation > The Table Module > Table - Embedding Examples".
To paraphrase the official docs though, if the Table finds itself with any module immediately downstream that has a group attribute matching "row.fields.someField", and it finds that it actually has a field called "someField" in the results it's rendering, then instead of rendering ordinary text as the contents of those tablecells, it will process and render the given module config. In this case we've given it just a simple HTML module, and as you can see we tell it to render a link in the tablecell instead.
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