If employees are watching the clock, it means one of two things:
1) Their kid/grandkid has a soccer game they need to get to or
2) Their work does not have a sense of mission, they are being micromanaged, or there is some other reason they want to get out of there.
More and more, the management emphasis is more on getting work done, rather than hours put in. If there is a sense of mission that is clearly communicated, and the employees feel involved in the mission, they won’t feel a need to watch the clock.
This is an oversimplification, but it rings true in my experience.