Part of Hampshire redeveloped by accident (6)
I believe the answer is:
mishap
'accident' is the definition.
(mishap is a kind of accident)
'part of hampshire redeveloped' is the wordplay.
I cannot really understand how this works, but
'part' could be 'mi' (mi is a kind of part) and 'mi' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
'by' is the link.
Can you help me to learn more?
(Other definitions for mishap that I've seen before include "Unpleasant accident" , "Unfortunate minor accident" , "Contretemps" , "An accident or unlucky event" , "Unlucky development" .)