Itinerant person (4)
(Other definitions for hobo that I've seen before include "Deer, situated at the back" , "Bum" , "Vagrant (US)" , "Vagrant (American)" , "American tramp" .)
'itinerant person' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for drifter that I've seen before include "One who moves about aimlessly" , "Bum" , "Vagrant - fishing boat" , "Ship - a tramp, possibly" , "fellow lacking direction" .)