Old civil orders to detain criminal set producing toxin (8)
I believe the answer is:
asbestos
'toxin' is the definition.
(toxic material)
'old civil orders to detain criminal set' is the wordplay.
'old civil orders' becomes 'ASBOs' (anti-social behaviour orders).
'to detain' is an insertion indicator (inserted letters are held or detained).
'criminal' is an anagram indicator.
'set' is an anagram of 'est'.
'asbos' enclosing 'est' is 'ASBESTOS'.
'producing' acts as a link.
(Other definitions for asbestos that I've seen before include "Fibrous mineral, used as an insulator, now deemed harmful" , "dangerous stuff" , "insulating material" , "Fire-resistant mineral" , "Fire-resistant material, a danger to health" .)