This is almost too easy. Anyone is easily recognized as the Fourth Doctor with only a floppy brown hat and a 12-foot long scarf. But the BBC has more deets, such as neckwear:

“A burgundy cravat, perhaps, or some kind of neckerchief, but the Fourth Doctor is not much of a formal tie-wearer”

Fun fact: The Doctor wore multiple scarves, according to The Doctor Who Scarf Recreation page, some as long as 20 feet.