Might or won't be eaten by the vegetarian (4)
I believe the answer is:
beef
'might' is the definition.
(thesaurus)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for beef that I've seen before include "Bovine flesh" , "Type of meat" , "it's unacceptable for vegetarian" , "Grouse - meat" , "Brawn; complaint" .)