Without knowing the model number of your front loading washer I will not be able to provide any model specific information, only general. First, I must assume the drain hose is not pinched or crimped. I must also assume the drain pump motor is operating and not jammed. Usually there is removable lower panel that will expose the drain pump and hoses. Some models have a removable pump filter cap that can be removed in order to clean debris from inside the drain pump and some models do not have pump filter. If the drain pump is running and not restricted then you will need to remove and check for a restriction in the drain hose.
I added the instructions in the image below for the two most common front load models. The first image is of a model that has no pump filter cap and the second and third images are the types with a pump filter and cap.
NOTE: Disconnect the power supply from the power source before removing the lower access panel.
I recommend resubmitting your question with the model number if the instructions I provided in the images below does not match your type of washer.