Restoring a Time Machine backup

Hi

I have a 2011 Mac Mini (with 128gb SSD) with El Capitan installed. I also have 2 external HDD's, a WD 2TB (Main Drive) and Seagate 4TB HDD (My Time Machine Drive).

The WD 2TB Drive has died and I want to use the Seagate 4TB drive as my main media drive until I can get a replacement. However 3.5TB of the drive is being used by Time Machine for the backup of the 2TB and 128gb boot drive.

I want to "restore" the Data from the Time Machine backup (about 1.5TB worth) onto the same drive but there is not enough space due to the Time Machine backups taking up most of the space

Any ideas?