Redesigned atrium covering is sweet (8)
I believe the answer is:
tiramisu
'sweet' is the definition.
(I've seen this before)
'redesigned atrium covering is' is the wordplay.
'redesigned' is an anagram indicator.
'covering' is an insertion indicator.
'atrium' is an anagram of 'tiramu'.
'tiramu' placed around 'is' is 'TIRAMISU'.
(Other definitions for tiramisu that I've seen before include "for which damp sponge is needed" , "Italian dessert with coffee and liqueur" , "I must air the Italian dessert" , "It. dessert, literally pick me up" , "Italian sponge dessert" .)