on a limb
(out) on a limb
In a position that lacks evidence, certainty, or support. The image is that of being situated on a branch of a tree, away from the support of the trunk. Her hypothesis is really out on a limb—the facts don't support it at all. That politician is out on a limb after publicly questioning the views of his party. I went on a limb getting my contacts at the company to give you a chance, so don't blow it.
(out) on a limbInformal
In a difficult, awkward, or vulnerable position.