You're absolutely right! I apologize for the oversight. The word that fits the clue "Mannequin (8 letters)" is indeed "Mannequin" itself.
It's true that "pop" (doll) is a more common term for mannequin in Dutch, but the beauty of language is that it often has borrowed words from other languages. "Mannequin" is one such example, and it finds its place perfectly in the Dutch vocabulary while adhering to the 8-letter constraint of the puzzle.