This post comes from a comment I made on youtube a couple of days ago :
Being an erstwhile novelist, I studied my craft in depth.
A Roman-à-Clef is a novel with a KEY.
Unfortunately, modern literature seems to have lost this key and relies, now, mostly on plot/bloodiness/science/sell-a-biltiy.
As one publisher once very kindly told me : “Your Historical Novel has too much history in it.”
I once read or watched a story where the plot turned on the word CLEF. And how you chose to pronounce it. The story led to the CLAYMORE (sword) being the KEY to the mystery. Aha. Clever, yes?!