Orange grated over herb (7)
I believe the answer is:
oregano
'herb' is the definition.
(I know that oregano is a type of herb)
'orange grated over' is the wordplay.
'grated' indicates anagramming the letters.
'over' becomes 'o' (cricket abbreviation).
'orange' is an anagram of 'oregan'.
'oregan'+'o'='OREGANO'
(Other definitions for oregano that I've seen before include "herbal preparation" , "Kitchen herb" , "Pizza herb" , "that's aromatic" , "Wild marjoram" .)