You can put one set of clothes ontop of another if: a: they are designed to layer anyway (like a set with a coat and a shirt) b: you can make the underneath clothes partly invisible (just check the invisibilty button for the relevant parts) c: you can scale the outer clothing up slightly to make it fit. It is kinda rare to need to do this, some outer clothes come with traces of the lower clothes already (example: a suit jacket may well have the shirt top and tie included).