A definition of ready is used to produce story readiness. A story which is ready for development needs to meet criteria. Thus criteria defined is required to accomplish a story. The definition of ready is an activity of the development team to state everything what's required before development begins. It is also a contract between development team, product owner and stakeholders. A development team has to contribute that the criteria is meet as far as possible. If criteria is missing from stakeholders or product owner the team should deny to start the work or close the gaps with own decisions and suggestions. The definition of ready is a tool to make explicit and transparent what is needed to start a story and can be used for developers as last line of defence.
The goal of a sprint is to deliver working software in the state of done. The delivery is called potential shippable product increment also known as usable software ready for installation.
To deliver a full working software due to your definition of done there are preconditions to be met before you can start your work. E. g. you might need several documents in advance like text, math and formulas, design and so on. On the other hand you as a development team need to specify which criteria has to be met to validate that you build the right software.
The battle and the sword
In order to complete a story within a sprint every part of the story must be delivered in time, otherwise the team might be wasting time with waiting during a sprint, will not deliver or will have to adjust the delivery later on. Furthermore, to avoid waste of specifying stories too early the timeframe of making work ready is set very close to development. To dissolve those contrary interests - that is the battle. Like in a shield wall you have to push forward and should not loose ground.
Cutting through dependencies in a tight schedule between preparing the work and implementing it is tough. On the one side you shield yourself against getting blocked and deny work which is not ready for action, on the other side you have to contribute to get the work ready and must be aware what is required to start. Both sides are the cutting edges of your sword.