Deep Rock Galactic

ORIGINAL SOLUTION:

Title is slightly misleading. You do not have to be in a mission for an hour or longer yourself, you just need to be in a mission that ends with the total mission time being an hour long or more.

Therein, to get this one quickly, you can join a game that's already in the works, that's close to or over an hour long, and get the achievement once the Mission is completed.

EDIT ON 3/10/2022

Comments below indicate that the trick above is not working for everybody (I've read a few threads about discrepancies between host and client timers that may be the cause of this, though I have no direct evidence). If you're one of the unfortunate ones that can't unlock the achievement with the trick above, you can easily brute force this achievement, abet it will take you an hour to do so.

Start a private solo mission, and select the easiest Mining Expedition you can (preferably Difficulty lvl 1, Length lvl 1, Complexity lvl 1). From here, complete the level to the point where you would summon the evacuation dropship, with the following changes:

1.) Use your pickaxe during the level as much as possible to avoid ammo use
2.) Let BOSCO do the majority of the shooting for you
3.) Be sure to mine all the Nitra you come across

Now, once you're at the point you'd normally summon the dropship, feel free to summon all the resupplies you can into your immediate area, and just wait for the mission timer to hit one hour. Between the healing and ammo the resupply pods offer, and the assistance of BOSCO, you should have no issues holding off the occasional bug wave. Once the hour hits, finish the mission and the achievement will unlock.

This can be done Idle and you don't need to finish the level to get the achievement.

Start a Solo game on any mission and have the Hazard Level set to 1 (Class does not matter). Once you enter the level DO NOT leave the drop pod from start, enemies do not enter the drop pod and the game does not kick you out of the pod either but the timer starts. After 1 hour of staying in the pod the achievement will unlock and you can leave the mission or complete it.

On Windows it does not kick you for not moving so I'm assuming it doesn't on console as well.

A straightforward way to do this is to pick up Engineer, dig a hole, go inside it, and close it with a stack of your platforms. You will get the achievement as soon as you hit the one hour mark.