Foolish libertarians cut bran out completely but it could make them very ill (8)
I believe the answer is:
listeria
'completely but it could make them very ill' is the definition.
I can't judge whether this definition defines the answer.
'foolish libertarians cut bran' is the wordplay.
'foolish' indicates an anagram (a foolish spelling).
'cut' indicates named letters should be taken away.
'libertarians' with 'bran' taken out is 'lietrias'.
'lietrias' anagrammed gives 'LISTERIA'.
'out' is the link.
Can you help me to learn more?
(Other definitions for listeria that I've seen before include "Dangerous food bacterium" , "Hazard in badly kept food" , "Micro-organisms associated with food poisoning" , "Is it real? (anag) -- kind of food poisoning" , "disease" .)