Hi Trish,
this is actually a good question. ClearCase UCM along with other robust version control systems are intended to allow you to commit changesets that cannot be removed. What you can do is create another changeset to reverse the changes that were delivered. I believe that you can use the cset.pl script in the IBM Rational IC Package. As explained in this link, the CSET.PL is a script to manage change sets in Rational ClearCase UCM
http://www.ibm.com/developerworks/rational/library/05/0927_bellagio/
Bob Aiello
Technical Editor