Sweet roll made with gusto by a professional cook lacks finish (7)
I believe the answer is:
brioche
'sweet roll' is the definition.
'brioche' can be an answer for 'roll' (brioche is a kind of roll). I'm unsure of the 'sweet' bit.
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for brioche that I've seen before include "Soft roll made of light yeast dough" , "Sponge cake or roll" , "Sweet yeast bread" , "Small French roll" , "Soft roll sometimes mixed with currants" .)