Burden a person usually carries (4)
I believe the answer is:
onus
'burden' is the definition.
(I know that burden can be written as onus)
'a person usually carries' is the wordplay.
'carries' indicates the answer is hidden within the clue.
'ONUS' can be found hidden inside 'a person usually'.
(Other definitions for onus that I've seen before include "Responsibilty" , "Duty or responsibility" , "Burden, duty" , "Encumbrance" , "'Burden, load (4)'" .)