In blessing, everything is swell (7)
I believe the answer is:
balloon
'is swell' is the definition.
(thesaurus)
'in blessing everything' is the wordplay.
'in' indicates putting letters inside.
'blessing' becomes 'boon' ('boon' can be a synonym of 'blessing').
'everything' becomes 'all' (I've seen this before).
'boon' going around 'all' is 'BALLOON'.
(Other definitions for balloon that I've seen before include "Inflatable - rapidly expand" , "Air-filled bag" , "Air transport" , "Brandy glass" , "Inflatable rubber bag, could be filled with hot air" .)