A chemical compound found in lethal identification (6)
I believe the answer is:
halide
'a chemical compound' is the definition.
(halide is a kind of chemical compound)
'in lethal identification' is the wordplay.
'in' indicates the answer is hidden within the clue.
'HALIDE' can be found hidden inside 'lethal identification'.
'found' acts as a link.
(Other definitions for halide that I've seen before include "Halogen compound" , "Chemical containing e g chlorine" .)