Coroner's investigation (7)
I believe the answer is:
inquest
'coroner's investigation' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for inquest that I've seen before include "Coroner's investigation" , "Coroner's inquiry into cause of death" , "Coroner's jury" , "Coroner's court" , "Post-mortem investigation" .)