Add another ../ to your address try this ../../Product/desc
or
I know what he means, I thought I just need to answer your question not providing any other approach,
<result name="YOUR RESULT NAME" type="redirectAction">
<param name="actionName">desc</param>
<param name="namespace">/Product</param>
</result>
Do not forger to precede the namespace name with a / otherwise it does not work. To redirect to an action in default package use / as your namespace param.