Used in autopsy, chemical spirit (6)
I believe the answer is:
psyche
'spirit' is the definition.
(psyche can mean spirit or soul)
'used in autopsy chemical' is the wordplay.
'used in' indicates a hidden word.
'PSYCHE' is hidden within 'autopsy chemical'.
(Other definitions for psyche that I've seen before include "Human soul or spirit" , "Immaterial part of a person" , "The soul, spirit or mind" , "Sole and spirit" , "Eros's beloved" .)