I have a conforming cloth in P7 and made in ZBrush3 a displacementmap and a texture map for this cloth. Back in P7 I want to apply these new maps. But .. there is no group which comprises the whole cloth (I made the maps for the whole cloth) . 
I do know how to make a new group and assign new material to it WITHIN an existing group, but I don't know how to make a new actual group (not subgroup)
So how do I get these maps functioning?

Well the normal thing is you apply the same shader to every material zone. It doesn't matter that they are different groups of polygons.

On the other hand, you could use the group tool to assign the same material zone to all the groups. Then you only have one shader to modify.

Open the group tool. Select each existing group one by one. For each, assign material to the same name. It can be an existing mat zone, or a new one you make up.

Hai Baggingsbill,
What you suggest would be a working way with a normal texture, in which every bodypart would get the same texture, but in this case I made a texture in ZBrush3 with very different paintings on the different parts of the whole texturemap. 
So it would help if I could define a total-prop group in Poser onto which I could apply this total-prop texture, isn't it? 
Or should I break down the texture into its bodyparts inside ZBrush and export these parts-textures apart?

I expect you would want to assign a material group that matches your displacement map, which (I think!) would be tied to the UVMap.  The material grouping is independent of figure object grouping, as in body parts.  E.g. in a typical clothing figure, you might have Chest/Abdomen/Hip, whereas there will normally be a "Cloth" or somesuch group that covers all the geometry that material applies to.  I think the mapping of material groups ought to be done on the Zbrush side, since that's where you're making the displacement map.

Thank you pjz99 for the suggestion,
I will look wether in my clothingfigure there indeed exists a general 'cloth'-group. 

Note that just because the material group is there, does not mean that Zbrush actually built your displacement map to comply with the map the material group is using - it may not fit correctly.  I don't know more than the most basic concepts about how Zbrush actually decides where your displacement map is going to correspond to your model, but I think that is something to be careful of (on my list of things to learn).

*but in this case I made a texture in ZBrush3 with very different paintings on the different parts of the whole texturemap
*Why did you do that? When somebody designs a skin texture - yes its going on 7 different groups, but it is the same texture. Similarly, if you're designing a body bump map, you only need one.

On the other hand, if you have different maps for each material zone, what is the problem? You should go to each material zone and load the correct map. Just like Jessi has a color map for face, and a different one for body, so you should have two maps.

And V3, who has different zones for arm, chest, etc, which use the same UV mapping, can be given the same maps, or different maps, depending on what you want to do. That's the point.

When you want red lips - you don't go into every face map and touch up the lips. You put a differen't face map on the lips zone. There is no limitation that says you must or musn't do it either way.

I'm really not understanding what the problem is.