Sonic umbrella

A sonic umbrella was a device used by aboard a Mondasian colony ship. The activation controls where located at the handle end opposite the emitter at the tip. It had multiple uses, namely how Missy used her umbrella to locate and call up a lift onboard the Mondasian colony ship, (TV: World Enough and Time/The Doctor Falls) close a metal door several feet away and could combine with the Doctor's Sonic screwdriver to create a barrier to hold a fully evolved Cyberman back while (using his Laser screwdriver) and a cyber-converted Bill Potts disabled it. It could also be used as an effective melee weapon, Missy using it to strike the Doctor the floor shortly after he gained an advantage over her younger self. (TV: The Doctor Falls)

Behind the Scenes
It is unknown if the sonic umbrella used by Missy in World Enough and Time and The Doctor Falls is the same umbrella that she had in Deep Breath, Dark Water and Death in Heaven.