Further to my last post, have been delving into John Clews a little further, and after searching around, found a copy of the Staffordshire General & Commercial Directory, published in 1818 by Parson & Bradshaw. This would have been shortly before John Clews died, and in it, there is a listing for Newcastle-under-Lyme for "Clews John & Son; maltsters and hat manufac. Merrill street."
I had found several references to a "John Clews" of Newcastle in various listings for parliamentary polls, and cited as a hatmaker, but it was not definitive that they were one and the same. In the final such poll, dated 1807, John Clews is listed as "Bailiff" and a "Returning Officer". In the Directory of 1818, John Clews is listed as an Alderman of the town and there's a Ralph Clews "Gent" on the Common Council. So, all ties up quite neatly.
In another similar directory, from 1834 (presumably just before the crash) I find Ralph & James Clews listed as Coalmasters, and owners of Jackfield Colliery. This, then, ties in with other records I have found of Ralph, after his bankruptcy, operating still as a Coalmaster.
Just to add spice to the mix, the earlier Directory lists another pottery manufacturer; Rivers & Clews, of Shelton, but I can't find out anything more about the company. Perhaps it was short-lived? Either way, it's another avenue to explore ....