What is the situation when my termporary contract does not have a termination clause?

Then the employment agreement cannot be terminated before the end date without the consent of the employer. But I would advise you to let a lawyer check your employment agreement since it would be unusual if it would not provide for a termination clause.

In addition to Boudewijn's comment I advise you to check if the contract is still in the probational fase (a "proeftijd"). If that is the case, then it is possible to terminate the contract. This is also so, if there are grounds to terminate the contract immediately ("ontslag op staande voet"). Next to these legal options, there is ofcourse always the option to "just" talk with your employer. In my experience - if there are no other reasons not to terminate the contract - employers rarely want to maintain a contract with an employee who is unhappy.