Thanks to paul atisto jack and spike for the votes - much appreciated.
Cheers for the challenge nemo - a tricky one.
As for the chemistry, well it's only a crossword clue isn't it ;) Maybe "alloy" might have been better but as pointed out it couldn't exist.
Perhaps they could synthesise an organic anion with a lead atom somewhere in it which would love to combine with the archetypal cation K+ ?