The CW (formerly known as The WB) was the original network that aired Charmed. The series ran for eight seasons from 1998 to 2006. TNT has never been associated with the show.
The episode you're likely referring to is "Witch Way Now?", where Gideon is killed by the Source of All Evil. This episode aired on The WB as part of the show's regular run.
If you have any further information about the episode or the context, feel free to ask.