noop $findfile(foldername, *, 0, write -c $1).shortfn

That'll clear all files in foldername and in any subfolders of it aswell. If you just want to clear the files in that specific folder use:
noop $findfile(foldername, *, 0, 0, write -c $1).shortfn

Note: $findfile() as used above will also return the number of files cleared if you need it.

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