Cluewords 91 Baffler

Have a few I can't get. Usually I get the Baffler out, but this one is hard. I could be in dopey mode though...
1. o7-10 Meltdown. Have G-C. Is it GFC. Also, whatever the middle letter is will give me the answer to Japanese persimmon. So far only have the last 2 letters, --YU.
2. Famous Bach piece. Have Ari-so.
3. Have S-sna for Russia's Don River tributary.
4. Have a clump in the bottom left corner: Have Sec for dry (wine) but can't get the castle upper room (have -o-ar) or the studio's outdoor filming area (have -o-) or the Roman orator (---o). Google keeps giving me Cicero.
Help is always appreciated. Many thanks in advance. T.