Treat indulgently with fine nosh, aromatically flavoured (7-3)

'treat indulgently' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.

'fine nosh aromatically flavoured' is the wordplay.
I cannot quite understand how this works, but
'fine' could be 'f' (abbreviation in pencil classifications) and 'f' is located in the answer.
'nosh' could be 'eat' (I've seen this in another clue) and 'eat' is found in the answer.
This may be the basis of the clue (or it may be nonsense).

'with' acts as a link.

Can you help me to learn more?