The word "gave" means to present or offer something to someone. "A thumbs-up" is a gesture where the thumb is extended upward, indicating approval, agreement, or satisfaction. So, "gave a thumbs-up" means to show approval or agreement by making the thumbs-up gesture.
Note: The provided meaning of the answer is for the latest New York Times crossword puzzle clue: Green-lit. Explanations are generated by AI and may be inaccurate.