Supplier's broth is nutritional at the core (8)
I believe the answer is:
stockist
'supplier's' is the definition.
(stockist is a kind of supplier)
'broth is nutritional at the core' is the wordplay.
I cannot quite understand how this works, but
'broth' could be 'stock' (synonyms) and 'stock' is present in the answer.
'is' is found in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is present in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for stockist that I've seen before include "Retailer of a particular line of goods" , "Shop that carries a particular item" , "Retailer carrying a particular item" , "dealer" .)