The crucial thing to realize is that an item isn't limited to have just one clothing type tag.
So if your full outfit, for simplicity's sake, consists of a tanktop, pants, and boots, give it the tags you have mapped to the clothing types "Tanktop", "Pants", and "Shoes".
When you're putting this outfit on, Wardrobe will look for all the clothing types to remove for the combined set of "tanktop", "pants", and "shoes", which should be everything that needs to be taken off since your outfit just consists of these three types.
Hence, there is shouldn't be any need for a "full outfit" clothing type.
As for the related comment: That's one way to do it if you prefer to add the individual parts as items to Wardrobe, although I wouldn't call it a fake entry, but rather take a photo of yourself wearing the full outfit.
In the future, there might be an outfit builder to piece an outfit together from individual Wardrobe items (there is a suggestion for exactly this in the suggestion box; if you like the suggestion, please feel free to vote for it).