A little banger is known to be a hazard (4)
I believe the answer is:
risk
'a hazard' is the definition.
(I know that hazard is a more specific form of risk)
'a little banger is known to' is the wordplay.
'a little' indicates a hidden word (a little bit of the clue).
'RISK' is hidden within 'banger is known to'.
'be' acts as a link.
(Other definitions for risk that I've seen before include "The possibility of danger - chance it" , "Take a chance" , "Expose to danger" , "Endanger, jeopardise" , "Possibility of bad outcome" .)