Jeeze Philip, where would you move it to? I know, I know, you can always move it to my house!!! :) Most peony do best with at least 6 hours of sun, but if it's blooming ok, and the lean doesn't bother you, I'd probably let it be. :) I still have 4 to dig and divide yet this year...

Diann
IA Z5a

Philip, Of course you would have to be the judge about any possible "other" place that can offer more sunlight but I think you should weigh any improvement and what it might do for any increased amount of bloom quality/quantity.

The leaning: Well, if not supported as the plant matures, peony will, its its nature to lean over, to even fall over with the amount of bloom on such a flimsy stem. I bet the flower weighs 3 times what the stem can hold upright.
So one must prepare beforehand so as to not spear any roots and new shoots that want to come up with stakes or wire cones or other means.

If you have nearby rigid forms, a fence, a tree, a stout stake outwards, then possibly just tieing some string loosely to support the stems and bloom can keep the plant up with its face to the sun.

It has not been my experience that peony will turn its head to increased amounts of sunlight....like some plants do.
(dahlia, and sunflower, for example). The plant produces such an overwhelming amount of bloom I don't think it turns its head to soak up more.

Of course the prime example of this twisting of one's head to the light is found in the Christmas Cactus.
Where this guy is moved from light it is accustomed to, it will literally twist its head off.