my experiment logic

you mean the actual code doing the training ?

so that it gets lazily executed and not at task definition time

Task definition time -> when creating the Pipeline Task? remember the base_task_factory a the end creates a Task object (it does not run the code itslef).
BTW: if you have simple training logic you can use pipeline decorators , it might be a better fit?
https://clear.ml/docs/latest/docs/fundamentals/pipelines#pipeline-from-function-decorator