Continuing on 2d, I did wonder about a chemical element as per witless@91, but think I favour Brendan's explanation @26 for 2d - actually a very elegant construction, but tough tough tough! ...And it leaves 'is it' superfluous AFAICS.
Much in common with pamd, I have 3d, 4d, 5d and 14a still to complete. I'm presuming we have an Aussie tucked into the guy at the market but nothing's occurring to me.
Thanks to all on this forum. I had bottomed out with six answers when I came here earlier today.