British and American transport (3)
I believe the answer is:
bus
'transport' is the definition.
(I know that bus is a kind of the transport)
'british and american' is the wordplay.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'and' says to put letters next to each other.
'american' becomes 'US' (abbreviation for United States).
'b'+'us'='BUS'
(Other definitions for bus that I've seen before include "People carrier" , "eg Double-decker" , "Coach" , "Road vehicle able to carry many passengers" , "Large passenger vehicle - small business!" .)