It was meant to be decorative, but came to nothing (5)
I believe the answer is:
cameo
But I can't explain it at all! Could you help me understand?
(Other definitions for cameo that I've seen before include "Item of jewellery with a portrait - distinguished actor's minor role" , "Piece of jewellery; small role" , "Small part for star actor" , "Jewellery item with carved portrait" , "Brooch with an engraving in low relief" .)