cane, stick
仗 centers on a long, slender object used for support or as a tool: a cane or stick. The idea is a handheld rod that aids walking or serves as a simple implement.
仗 combines 亻 (person) with 丈, which likely contributes both sound and the idea of a length or measure, suggesting a person holding a long stick or cane.
A person 亻 holding a long measuring stick 丈: that stick becomes their cane for support.
For ジョウ, imagine a person leaning on a cane while watching a show: show -> ジョウ, and the cane supports them through the performance.