A progress clock is a stress-track used to track ongoing effort against an obstacle or to model the approach of impending trouble.
Sneaking into a guarded outpost? I might make a progress clock to track the alert level of the patrolling guards.
Any time the PCs suffer consequences from partial successes or missed rolls, one or more boxes on the progress clock might get marked off. When the stress-track is full? The alarm might go off!
A clock tracks progress in overcoming an obstacle, not the method used to overcome that obstacle. Clocks for an infiltration might be “Interior Patrols” and “Digital Locks.” The patrols and the locks are the obstacles. How you overcome them is entirely up to you.
Complex threats might have several “layers,” each with its own progress clock. For example, the gangs’ HQ might have a “Perimeter Security” clock, an “Interior Guards” clock, and an “Office Security” clock.
The crew would have to make their way through all three layers to reach the gang boss’ personal safe and valuables within. Remember that a clock tracks progress. It reflects the fictional situation, so the group can gauge how they’re doing. A clock is like a speedometer in a car. It shows the speed of the vehicle—it doesn’t determine the speed
The GM can use a clock to represent a progressive danger, like the growing suspicion during a seduction, the proximity of pursuers in a chase, or the alert of a system being hacked or guard patrols being bypassed.
In this case, when a complication occurs, the GM ticks one, two, or three segments on the clock, depending on the consequence level. When the clock is full, the danger comes to fruition—the guards hunt down the intruders, activate an alarm, release the killer drones, etc.
Adapted lightly from Scum & Villainy RPG