An open ended barrel, I am shaped like a hive. I am filled with the flesh, and the flesh is alive! What am I?

Why this works

This riddle plays with the double meanings of certain words. The "open-ended barrel" refers to the thimble's shape, which is cylindrical like a barrel but open at the top. The phrase "shaped like a hive" points to the thimble's texture, which often has dimples resembling a honeycomb. Finally, "filled with the flesh" cleverly refers to the fact that when sewing, a thimble is used to protect your finger (the flesh) while pushing a needle through fabric, making it feel "alive" with action. Thus, the thimble is the answer, beautifully tying together these playful images!