Gosh! Thanks for the votes, FJ, pigale, AB and busby, and the mentions, paul, BBM2, ginge and rossim.
Thanks for running the show, SW, and the clips - nice songs (which, indirectly, have helped me pick next week's challenge).
The clue was actually my first thought, but, as a chemist, I thought the definition was too loose, so I went for the one that ginge helpfully pointed out was incorrect - thanks for that, ginge!