Full of non-vegetarian substance (5)
I believe the answer is:
meaty
'full' is the definition.
(thesaurus)
'non-vegetarian substance' is the wordplay.
I cannot really see how this works, but
'substance' could be 'meat' (meat is a kind of substance) and 'meat' is located in the answer.
A single letter 'y' remains which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'of' acts as a link.
Can you help me to learn more?
(Other definitions for meaty that I've seen before include "Fleshy, or full of informative matter" , "Full of substance, nourishment" , "Brawny; full of substance" , "Hearty" , "Full of substance, flesh" .)