Yellow plate (6)
I believe the answer is:
chrome
This clue is a double definition.
'yellow' is the first definition.
(chrome yellow is a kind of yellow)
'plate' is the second definition.
(I know that chrome is a more specific form of the action plate)
(Other definitions for chrome that I've seen before include "Decorative plating" , "Feature of bath taps" , "shiny stuff" , "Shiny metallic plating" , "Protective finish on motor vehicle fittings" .)