Toxin involved in scare (7)
I believe the answer is:
arsenic
'toxin' is the definition.
The answer and definition can be both substances as well as being singular nouns.
Maybe you can see an association between them that I can't see?
'involved in scare' is the wordplay.
'involved' is an anagram indicator (involved can mean confusing or complex).
'in'+'scare'='inscare'
'inscare' anagrammed gives 'ARSENIC'.
Can you help me to learn more?
(Other definitions for arsenic that I've seen before include "-- and Old Lace (play)" , "Poison found in races" , ", it goes with old lace" , "killer" , "Poisons in scare" .)