How to refer to a parent folder

I’m trying to right a action in my script to refer to a “parent” folder. By parent folder I mean a folder who is one level up from the folder I put in a variable.

Exemple:
I script "set x to every folder of entire content of disk_x whose name ends with “_4”
then I find this folder : x = folder_4
now I whant to refer to is parent folder the folder who contain the “folder_4” and put it in a variable. How can I script that if I dont know where the “folder_4” is.

Tanks for your help

Something like this should work.

tell application "Finder"
	set parent_ to container of folder_4
end tell

– Rob