Misrepresented upper house, perhaps, in glossy material (6)
I believe the answer is:
sateen
'glossy material' is the definition.
(I've seen this in another clue)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for sateen that I've seen before include "Glossy material" , "Shiny cloth used for furnishings" , "Sea net could provide a glossy fabric" , "Cotton fabric with a satiny finish" , "Shiny cloth found in senate" .)