Way in which unfinished story makes one scoff (7)
I believe the answer is:
lasagne
'one scoff' is the definition.
(scoff can mean food)
'way in which unfinished story' is the wordplay.
'way' becomes 'lane' (lane is a kind of way).
'in which' means one lot of letters goes inside another.
'unfinished' means to remove the last letter.
'story' becomes 'saga' (a saga is a long story).
'saga' with its final letter taken off is 'sag'.
'lane' going around 'sag' is 'LASAGNE'.
'makes' is the link.
(Other definitions for lasagne that I've seen before include "Flat sheets of pasta" , "Course" , "Italian sheets" , "continental dish" , "Layered pasta dish" .)