A step is an action or process that is part of a larger activity or task. In the context of the clue provided, "Pierce film with fork" is possibly the first step or initial action in a series of steps. It means to make small holes in a thin layer of material (such as a film) using a fork.
Note: The provided meaning of the answer is for the latest New York Times crossword puzzle clue: Accelerate, with "up". Explanations are generated by AI and may be inaccurate.