Thin glossy silk fabric (7)
I believe the answer is:
taffeta
'thin glossy silk fabric' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for taffeta that I've seen before include "Sheeny fabric" , "Thin silky material" , "Shiny fabric for fat fate" , "Fine crisp silk fabric" , "Smooth, stiff fabric" .)