The clause is known as 'condition precedent'.
Step-by-step explanation:
When a contract, especially that of the sale of a property is made, the conditions mentioned for the fulfilment of the agreement are known as 'conditions precedent'.
These conditions need to be fulfilled before the deal is sealed by the party that is mentioned to be responsible for its fulfilment in the contract. Only once these conditions are fulfilled, the proceedings of the deal can be taken forward.