Trouble about to be noticed in posh vehicle or more ordinary one (7)
I believe the answer is:
railcar
'more ordinary one' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'trouble about to be noticed in posh vehicle' is the wordplay.
'trouble' becomes 'ail' (synonyms).
'about' becomes 'ca' (circa).
'to be noticed in' means one lot of letters goes inside another.
'posh vehicle' becomes 'RR' (Rolls Royce).
'ail'+'ca'='ailca'
'ailca' inserted inside 'rr' is 'RAILCAR'.
'or' is the link.
(Other definitions for railcar that I've seen before include "vehicle on the line?" , "Small train" , "It's found on tracks" , "coach" , "Passenger vehicle" .)