well, it depends how you backed up your system HD using CCC.
Did you make a bootable backup?
If you only want to restore Addictive Drums you need to find the locations of all the folder and files related to Addictive Drums on your external drive.
Select those in CCC and choose to copy / clone them to your Mac HD.
I can't give any further info on Addictive Drums as I don't have a copy of it - so I don;t know the locations, but generally you'll find the AU component file in:
check both the user account and the system library.
For important software I'd recommend either restoring your entire system or installing from the installation DVDs