Vehicle -- burden put on one (4)
I believe the answer is:
taxi
'vehicle' is the definition.
(taxi is a kind of vehicle)
'burden put on one' is the wordplay.
'burden' becomes 'tax' (I've seen this in another clue).
'put on' means one lot of letters go next to another.
'one' becomes 'i' (Roman numeral).
'tax'+'i'='TAXI'
(Other definitions for taxi that I've seen before include "(Of a plane) move slowly on the ground" , "Rank occupant" , "Danny DeVito sitcom" , "use apron" , "Public service vehicle" .)