Hey, good question.
You begin the battle by making two clocks that the players will fill with successful actions: the field clock (representing routing the enemy forces) and the foe clock (representing eliminating the enemey commanders). When (and if) these clocks are full, the players win the battle. You could totally make a racing clock to track when the player retinue's forces are routed and tick that when the players' forces are routed. We aren't too prescriptive on how you frame the consequences for these rolls.
The fallout clock comes out after the battle is resolved, representing the aftermath of battle: "wraiths emerging, fires spreading, and structures collapsing". The players can resolve these, and potentially face consequences, or they can ride home. Choosing to not manage the fallout is likely to mean that the players will face more severe unrest and entanglements after this fight.
All that said, battles tend to be a rare thing. Most playtest groups only ran a few battles over the whole campaign. Most smaller skirmishes can be resolved in a single roll or pair of racing clocks. These rules are designed to give more detail and time to epic conflicts.