When setting expectations, the great manager explains the "why" behind the task. This helps generate buy-in and enable autonomy. So what is a manager to do when the why is different in the short run vs. the long run?
There are many examples of this, but I will pick a simple one. The software that runs the point-of-sale system for an organization is bad. It needs to be replaced. However, that is a long and expensive proposition. It may make sense, from an organizational perspective to spend money or resources elsewhere, but that doesn't solve the software issue right now. Usually, the team develops a work around or alternate system. What you hear from employees is questioning about why they are doing that and wasting time when what is really needed is a new system.
Making matters worse, the manager may not even have the exposure to higher decision making to know whether the new system is coming eventually.
This requires the manager to really explain 2 whys that are inter-related. First, why aren't we making the bigger, more permanent fix. Second, the why to the work around to fix the issues that is occurring right now.
What is important to remember is that you aren't explaining the why so they agree and approve (these aren't consensus decisions). You are offering the why so you can move forward.