I'm not sure if this is what your after....
Blog Setting -> Advanced ->Go down to Meta Data...
Short Description:
or/and
Post footer in RSS/Atom:

Apologies if I'm on the wrong track :)

Thanks John, but no that's not what I'm after. I need a single description for the feed that will display in a feed reader. I found it when I first installed my current version but didn't realise the full significance and made no entry. Now I've mislaid it.

admin > blog settings > [blog] > advanced .... meander down to short description ;)

¥

¥åßßå wrote:

admin > blog settings > [blog] > advanced .... meander down to short description ;)

¥

I meandered. But I thought I'd seen a box that was specifically for the feed description as distinct from the meta description. Maybe I was mistaken somehow. If so, my apologies and thanks.