No car, but a start in business (3)
I believe the answer is:
bus
'business' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'no car but a start' is the wordplay.
'no' indicates named letters should be taken away.
'car' becomes 't'.
'a start' becomes 's' (this might be a standard abbreviation I've not previously seen).
'but' with 't' taken away is 'bu'.
'bu'+'s'='BUS'
'in' is the link.
Can you help me to learn more?
(Other definitions for bus that I've seen before include "Charabanc" , "Coach" , "Large passenger vehicle - small business!" , "Motor-coach" , "Public service vehicle" .)