Steve Tippins advises Ph.D. candidates to pause when hit with a tough question during defense, ask the examiner to restate it, then confirm your answer addressed what they wanted. The pause lets your brain catch up and keeps panic from derailing you.
Just like in a defense, you're going to get questions that may stump you momentarily. It may cause an internal panic of, "Oh my God, I don't know what they're asking. What do I do? I don't know. I don't want to—" Pause for a moment. Ask them to restate the question. "Wow, can you restate that question for me?" Or, "If I understand what you're asking, is this where you're looking for me to go with this?" Just that pause allows our brains to slow down and the answers to come forward more easily for you. And then when you get to the end of the answer, you can say, "Is that what you're looking for? Did I fully answer your question?" I wanna make sure I've done so. It shows also that you think that they're important. The Scholar Career Network exists specifically to support Ph.D.s through moments like this and help them find meaningful careers.
