First and foremost a sub’s responsibility is to please their dominant. I know that is a pretty blanket statement but it is more than that. It means following rules. Doing as asked and respecting their dominant. Pre-emptive service is also something that pleases most dominants.
This is all important but a sub also has a responsibility to do self care. So cleaning themself and making sure that they present the image their dominant wants to present to the world.
Normally when I serve a Domme it means cleaning, but doing whatever they set as a task seems more appropriate, be it making coffee or cleaning out a litter box or both at once. If doing so makes their life easier then it is worth doing. This is what submission is in my mind.