Working on self-confidence finally failing, a sickener (6)
I believe the answer is:
poison
'a sickener' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
'working on self-confidence finally failing' is the wordplay.
'working' becomes 'on' (on can mean working or activated).
'on' means one lot of letters go next to another.
'self-confidence' becomes 'poise' (I've seen this before).
'finally failing' means to remove the last letter.
'poise' with its last letter taken off is 'pois'.
'on' put after 'pois' is 'POISON'.
Can you help me to learn more?
(Other definitions for poison that I've seen before include "Dangerous substance" , "Eg, strychnine" , "It causes illness or death in a living organism" , "Venom, harmful substance" , "Venom, toxin" .)