Puzzle over people carrier (5)
I believe the answer is:
rebus
'puzzle' is the definition.
(type of visual puzzle)
'over people carrier' is the wordplay.
'over' becomes 're'.
'people carrier' becomes 'bus' (I've seen this before).
're'+'bus'='REBUS'
(Other definitions for rebus that I've seen before include "Picture-puzzle" , "Word-picture puzzle" , "Puzzling device" , "Pictorial pun - fictional detective" , "Problem" .)