Hi Malone, thanks. I have solved the clue and worked out what the replacement must be (mainly thanks to this thread, ditto several others). Just having problems linking the two. I'll follow up on the Shakespearean angle.
As Gitto says, there's been a lot of fruitless delving but, on the other hand, I am now replete with useless knowledge. eg thanks to Brewers I now know that Harlequin may be a corruption of Erl King. Not sure how I'll use the info but browsing Brewer's is fun 😊