I had a clarks interview well over two (maybe almost three) years ago now so not sure what its like during covid. It was a group interview tho and I remember they asked us a bunch of questions about the store like what did we know about it, about ourselves etc. Ans then we had to go around the store and pick a pair of s***s each and have to "sell" it to the interviewer. I remember I picked up some smart flats with a strap that were comfortable and easy to walk in but also smart enough for work.
Just wear some comfy but smart clothing - black s***s, black trousers & a nice smart top.
A great website to look on for more info about other people interviews with them is Glassdoor, defo check it out. Its what I use before any interviews I go to.
Just an FYI - I did not get the job with clarks though so not sure about the 1-2-1
Good luck!!
EDIT: I don't know why it is censoring the word s h o e s ??