Millions consume what vegetarians won't (4)
I believe the answer is:
meat
'vegetarians won't' is the definition.
I can't judge whether this definition defines the answer.
'millions consume' is the wordplay.
'millions' becomes 'm' (abbreviation).
'consume' becomes 'eat' (eating is a kind of consuming).
'm'+'eat'='MEAT'
'what' acts as a link.
Can you help me to learn more?
(Other definitions for meat that I've seen before include "Spam, ham, lamb etc" , "17 [ESSENCE]" , "Animal flesh as food" , "Ham, pork, chicken etc" , "The flesh of animals as food" .)