Last piece of Arctic roll for dessert (7)
I believe the answer is:
crumble
'for dessert' is the definition.
'last piece of arctic roll' is the wordplay.
'last piece of' suggests the final letters.
'roll' becomes 'rumble'.
The last letter of 'arctic' is 'c'.
'c'+'rumble'='CRUMBLE'
(Other definitions for crumble that I've seen before include "Break up - pudding" , "Type of pudding - disintegrate" , "(To) fragment; pudding" , "Break up - fruit dish" , "Fall to pieces - dessert" .)