Do you want to actually delete the tracker and all its associated data? Or do you want the tracker to not show on your profile page?
For the first, go to your tracker. Click the Trackers icon on the right side of the tracker toolbar. This should bring up a list of all available trackers that you can add as well as trackers you have that you can delete.
If you want the tracker to not show on your profile, go to your tracker. Then click Tracker Settings. From there, you can make it public, private, or friends only. If you set it to private, it won't show up in your profile. If you have a tracker with a ticker, you can edit your ticker settings by clicking on the Configure Ticker link.
Hope that helps!
-MedHelp