Puzzle about vehicle (5)
I believe the answer is:
rebus
'puzzle' is the definition.
(type of visual puzzle)
'about vehicle' is the wordplay.
'about' becomes 're' ('re' means regarding or about).
'vehicle' becomes 'bus' (bus is a kind of vehicle).
're'+'bus'='REBUS'
(Other definitions for rebus that I've seen before include "Pictorial wordplay" , "Visual wordplay - Rankin's inspector" , "that's puzzling" , "Puzzling symbols, etc" , "Problem" .)