This page of the FF7 Remake guide has a description of Weapons on a Rampage side mission, available in Chapter 8 - Budding Bodyguard.
A frightened man asks for your help. The man was attacked by Shinra's defective weapons roaming the area. Move to the designated place and you will encounter the Mark II Monodrive. These enemies can e.g. surround themselves with a barrier and are really resilient to physical attacks, so you have to use Materia.
After eliminating the first group, search the area for the next one. The fight looks the same as before - you shouldn't have much trouble.
Reward: A pair of protective boots (give resistance to Slow and Stop).