Zesty thing, failure (5)
I believe the answer is:
lemon
This clue might be a double definition.
'zesty thing' is the first definition.
The answer and definition can be both human attributes as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'failure' is the second definition.
(lemon can mean a failure or useless person)
Can you help me to learn more?
(Other definitions for lemon that I've seen before include "Melon is another fruit" , "Strong yellow colour" , "Shade of yellow - fruit" , "Feeble thing (colloq.); fruit tree" , "Washout" .)