Cake decoration, almost heavenly (7)
I believe the answer is:
angelic
'heavenly' is the definition.
(relating to angels or heaven)
'cake decoration almost' is the wordplay.
'cake decoration' becomes 'angelica' (angelica stalks are used to decorate cakes).
'almost' means to remove the last letter (most of the word but not all of it).
'angelica' with its final letter removed is 'ANGELIC'.
(Other definitions for angelic that I've seen before include "Exceptionally innocent" , "Extremely well-behaved" , "Seraphic, cherubic" , "Sweet, kind and beautiful" , "Exceptionally beautiful" .)