Teaser concerning transport (5)
I believe the answer is:
rebus
'teaser' is the definition.
(I have seen 'Pictorial teaser' mean 'rebus' so perhaps 'teaser' could also mean 'rebus')
'concerning transport' is the wordplay.
'concerning' becomes 're' (both can mean on a particular topic).
'transport' becomes 'bus' (bus is a kind of transport).
're'+'bus'='REBUS'
(Other definitions for rebus that I've seen before include "Picture and word puzzle" , "Ian Rankin's Scottish detective" , "that's puzzling" , "Enigmatic representation" , "Picture-letter puzzle" .)