Herb's divine first of all (8)
I believe the answer is:
angelica
'herb's' is the definition.
(angelica is a kind of herb)
'divine first of all' is the wordplay.
'divine' becomes 'angelic' (I've seen this before).
'first of' indicates taking the first letters.
The first letter of 'all' is 'a'.
'angelic'+'a'='ANGELICA'
(Other definitions for angelica that I've seen before include "Candied stem, decorates cake" , "Its candied leaves are used in cake decoration" , "Candied plant stalks" , "Decorative candied stalk" , "Candied stalks used for cake decoration" .)