Daft criminal reports substance (7)
I believe the answer is:
silicon
'substance' is the definition.
(I know that silicon is a type of chemical element)
'daft criminal reports' is the wordplay.
I cannot really understand how this works, but
'criminal' could be 'con' (short for convict) and 'con' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for silicon that I've seen before include "Semiconducting element" , "Element found in chips?" , "Non-metallic element, symbol Si" , "Semi-conducting non-metal" , "Element occurring in sand" .)