If you're talking about those little edges that seem to be appearing, what I think you're running into is the fact that the mesh of that top is not actually a smooth surface - it's a collection of polygons, and I think you're seeing the edges of the polygons because of the way the garment is reacting to the pose, shape morphs, etc.
To prove whether this is the case, you could switch your viewport to "Wire Shaded" or "Wire Texture Shaded" and move in close, which should let you see the polygons themselves. If those are the edges of polygons, it ought to be fairly obvious.
So, how to fix this.
- You could add a smoothing modifier to the garment. This will tend to even things out a bit by reducing the tendency of the mesh to buckle.
- You could increase the subdivision level of the garment. (Parameters pane : "General / Mesh Resolution" underneath the garment. Try bumping the "Render SubD" up by 1 or 2. (each one you increase it will double the number of polygons, so increasing by 2 means polygons are 1/4 the size. Thus, don't go crazy, or you'll create a LOT of polygons.)
Or, possibly, do both.
The shot below shows what I mean. ("Wire Texture Shaded" view) The black lines show the actual polygons, with the finer lines showing subdivisions. The garment can only really bend along the lines, so if things are coarse, you can get odd-looking folds sometimes. Increasing the subdivision helps this, but, of course, it also increases the number of polygons, which takes somewhat more memory when you go to render. (Usually the size of the textures dwarfs the size of the mesh, however.)
