Blender is a way to go. General workflow:

Save all materials for cloth which you need to amend. Save Project.
Export to FBX with Blender option, as Mesh only, uncheck "Embed Texture". This would create an FBX key so you can bring avatar back to CC.
Import to Blender, do what you need to do with piece of cloth fixing the problem.
Export out of Blender overriding original import (just easier to have FBX key loaded automatically). All default setting except uncheck "Add Leaf Bones" in Armature section.
Import back to CC with "Create Cloth, Hair, Acc (with FbxKey)". Make sure to select the same layer number for amended cloth at the prompt.
Save amended cloth.
Load original project.
Apply amended cloth (overriding existed).
Reapply saved materials to the amended cloth.
Done!