Not at all happy with this one. Thanks Lie-in King will keep looking and if I get a brainwave will let you know - please do the same - I do like to understand!
I put 'spectrum', 'doublet' and 'stiffening' into 'google' and there is a definite connection between the three words.I couldn't make head nor tail of it but you may like to try. I'm going for 'spectrum'. Incidentally ,why are there so many winners of the Polymath crossword who live abroad? I'm not xenophobic,just curious.
Regarding the winners, over time there appears to be a "Rest of the World" winner one week, followed by a British winner the next. This is for Polymath only, the cryptic crossword is mainly British (and 3 of them). I have won the polymath once and the cryptic twice. Stopped sending in cryptic until prize changes again.
Keep sending it in you can win, but it might be best to send in when it is the "british winner" week.