Bran thought about it. 'Can a man still be brave if he's afraid?''That is the only time a man can be brave,' his father told him.

This quote is talking about how bravery is not about the lack of fear, but about what we do when we are afraid. The father is telling Bran that real bravery comes from facing a challenge and confronting fear, not from an absence of fear. In other words, it takes courage to do something even when we are afraid.