If the string to remove is this, and lets assume there is a closing tag as well
PHP Code:
<a href="13th_Black_Crusade" title="wikilink"></a>
Your search regex would be...
PHP Code:
<a href=".*?" title=".*?"></a>
.*? = anything between the two quotation marks
But if there is something between the opening and closing tag that you need to save, you would use...
PHP Code:
<a href=".*?" title=".*?">(.*?)</a>
and in the replace box you would use...