What does single ally mean? The one people ask in clan forums?
I know this is silly to ask but Im just curious

Single allies are people who can post in a clan without the need to use invade tags. It's like asking for letting them post in the clan board/DSC.

basically it's just a friend of the clan who just say's hey and whatnot every now and again

Oh so thats what it does.
Ok thanks for the help.

While you're not really meant to even use invade tags these days (Staff got sick of them apparently) It does allow a singular person to post in your clan without the fear of invoking invasion rules. Be warned though, they can be considered as members activity wise and if you have a bunch of inactive single allies it can make your clan look bad.