Hi there OP,
I see you've made your decision but wanted to post to reassure you. I could have written your post three years ago - my daughter was exactly the same, incredibly clingy, wouldn't let anyone else hold her other than me and her dad (and she wouldn't always settle with him). If anyone else looked after her even for a minute while I left the room, she'd immediately start crying, even with my mum, who she saw all the time. And like your daughter, she would only nap on me - I carried her around in a sling for about 9 months, it nearly killed my back!
I was desperate to go back to work but couldn't for the life of me see how this would be possible, I just blindly hoped that I would find someone who she would magically feel comfortable with. And do you know what? I did. I saw lots of childminders and nannies (like you, I ruled out nursery early on). With most of them she did cry when I left, experimentally, for a few minutes - but with one nanny she was absolutely fine. I have no idea why - I don't know what was different about her, but I watched my daughter sit happily in her arms, listened from the other room as she DIDN'T cry... I honestly felt like I was witnessing some kind of miracle!
Of course, much of it was down to the fact that her (now ex-) nanny is a lovely person - kind, gentle and nurturing. Unfortunately she's no longer working as a nanny or I would offer you her details!
Anyway, just to say that you may need to start early and meet with a fair number of carers, but I bet you'll find someone who has that magical effect on your baby, and things will work out. Also, as others have said, a year-old baby really is very different from a 6-month-old one, and the older they get the easier they find these things. My daughter took a little while to settle into nursery at 18 months, but now she loves it, and is hugely excited about starting preschool in September. And the legacy of a 'clingy' baby, in my case at least, is that she's turned into a super-cuddly, very affectionate 3-year-old, which I love. Good luck! I hope it all works out - I have confidence that it will.