A fedora was a hat.
Such a hat was part of the Fourth Doctor's outfit. (TV: Robot) He occasionally used it to cover his face to nap. (TV: Robot, The Androids of Tara)
The Seventh Doctor wore a paisley banded white fedora (PROSE: White Darkness) that he had had made especially for him. (PROSE: First Frontier)
When the Twelfth Doctor visited Las Vegas, he donned a fedora at Clara Oswald's insistence. (COMIC: Gangland)