Substance or content (4)
I believe the answer is:
meat
I believe this clue is a double definition.
'substance' is the first definition.
(I know that substance can be written as meat)
'content' is the second definition.
(I know that meat is a type of content)
(Other definitions for meat that I've seen before include "Edible flesh" , "Animal flesh as food" , "Food for carnivores" , "The flesh of animals as food" , "Flesh for eating" .)