Would some kind soul parse this little piggy to help give me closure? i think I might have the answer, and can vaguely see most of it, but not the whole damn thing...
27ac) Silas serving Opus Dei's condition in stopping French town's Mass (8)
I have A?B?N?S, and it looks like ALBINISM, but I still would not put money on it.
Aha! Ah, so! And having now just Googled the whole of the first bit I now see why maybe, just maybe, I ought to try again to read the Da Vinci Code. I had my brain stuck on Silas Marner. Doh! Many thanks, roslyn251254