How to delete Time Machine Backups that were moved into Recycle Bin Trash?
Solution 1:
If the drive is getting close to be being full, TM will free the space automatically.
You can empty the Trash (delete the files) much faster with Terminal command
rm -rf ~/.Trash/*
However, you will probably corrupt your entire backup by deleting specific TM snapshots (folders with datetime in the name). Learn how TM is actually storing the data on the drive (hint: symlinks).