Good man with rustic source of lemon dessert (7)
I believe the answer is:
strudel
'dessert' is the definition.
(I've seen this before)
'good man with rustic source of lemon' is the wordplay.
'good man' becomes 'st'.
'with' is a charade indicator (letters next to each other).
'rustic' becomes 'rude'.
'source of' says to take the initial letters.
The initial letter of 'lemon' is 'l'.
'st'+'rude'+'l'='STRUDEL'
(Other definitions for strudel that I've seen before include "Baked dish" , "Pastry with filling (usually apple)" , "German dessert" , "German pastry dish" , "A German baked pastry" .)