Giving marrow plus olde-worlde morsel (5)
I believe the answer is:
viand
'olde-worlde morsel' is the definition.
The answer and definition can be both things that one consumes for nourishment as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'giving marrow plus' is the wordplay.
'giving marrow' becomes 'vi' (I can't explain this - if you can you should give a lot more credence to this answer).
'plus' becomes 'and' (I've seen this in another clue).
'vi'+'and'='VIAND'
Can you help me to learn more?
(Other definitions for viand that I've seen before include "loaf of bread, maybe?" , "something to eat" , "Meat; article of food" , "Item of food (arch.)" .)