They are what they eat - literally (9)
I believe the answer is:
cannibals
'they' is the definition.
Both the answer and definition are plural nouns.
Perhaps you can see a link between them that I don't see?
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for cannibals that I've seen before include "Eaters of humans" , "Human flesh eaters" , "Animals that eat their own kind" , "People who eat people" .)