Not sure if I got your question right, but you could simply copy the song, and clear the track on the copy. You can then return to the original if you're not happy with your 2nd take.
Another way is to export the track, and then import it back when needed. The export/import functionality is generally meant for exchanging data with a computer, but sometimes I use it as a mean to back a track up.
(I have an DP-008EX, but looking at DP-006's manual, it should work the same)
