Such people going by car would be a bloomer (6)
I believe the answer is:
nation
'such people' is the definition.
'nation' can be an answer for 'people' (I've seen this before). I'm not sure about the 'such' bit.
'going by car would be a bloomer' is the wordplay.
I cannot quite understand how this works, but
'going' could be 'on' (both can mean functioning or activated) and 'on' is found within the answer.
'by' could be 'at' and 'at' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for nation that I've seen before include "Country, state" , "People of a state" , "American Indian people" , "People sharing a common culture/descent" , "The Birth of a -, D.W. Griffiths film" .)