Transport market rising? About right (7)
I believe the answer is:
tramcar
'transport' is the definition.
(tramcar is a kind of transport)
'market rising? about right' is the wordplay.
'market' becomes 'mart' (synonyms).
'rising?' says the letters should be written in reverse (in a down clue, letters go up).
'about' becomes 'ca' (circa).
'right' becomes 'r' (abbreviation).
'mart' written backwards gives 'tram'.
'tram'+'ca'+'r'='TRAMCAR'
(Other definitions for tramcar that I've seen before include "Passenger vehicle running on rails" , "Electrical vehicle" , "Public street transport on rails" , "Electrically driven public transport vehicle" , "Electric transport" .)