Decorative strip of fabric (6)
(Other definitions for ribbon that I've seen before include "Long strip of fabric" , "Long, narrow band" , "Narrow strip of coloured cloth, worn as ornament" , "Material tied in a bow, perhaps?" , "Headband" .)
'decorative strip of fabric' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for riband that I've seen before include "strip of fabric" , "Four across - is trophy for fastest Atlantic sea crossing" , "decorative strip" , "Strip of material" .)