Frustration tolerance is the ability to withstand obstacles and stressful situations.
That's what it is. Basically, the employee foresees stress in your job and wants you to be able to handle it.
If this is acceptable and normal depends on the employee, and is usually impossible to judge from the outside. I personally work in IT, and stuff often doesn't work as you'd like it too on the first try. Or a coworker get's sick and you do have to pick up his work, with deadline attached.
Stuff like that happens and is normal.
Some companies overdo this and expect the impossible in the name of you must "be frustration tolerant", like picking up your sick coworkers work and expecting to finish it on top of your work while holding both deadlines, both of them estimated with too much optimism to begin with...
But you usually you will only find out during interview or after joining the company.
When I personally see this in a list, I just tend to ignore it as company speak and apply anyway.