Wild kale is no good for those who want a silly panacea (5,3)
I believe the answer is:
snake oil
'good for those who want a silly panacea' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'wild kale is no' is the wordplay.
'wild' indicates an anagram.
'kale'+'is'+'no'='kaleisno'
'kaleisno' is an anagram of 'SNAKE-OIL'.
Can you help me to learn more?
(Other definitions for snake oil that I've seen before include "this won't make things better" , "Miracle cure" , "Liquid sold as medicine but medically worthless" .)