Mechanics arranged accident (9)
I believe the answer is:
mischance
'accident' is the definition.
(mischance is a kind of accident)
'mechanics arranged' is the wordplay.
'arranged' indicates an anagram.
'mechanics' is an anagram of 'MISCHANCE'.
(Other definitions for mischance that I've seen before include "Unfortunate business" , "Ill fortune" , "Unfortunate occurrence" , "Misadventure, mishap" , "Bad luck" .)