Also contains, I understand, flavouring (7)
I believe the answer is:
aniseed
'flavouring' is the definition.
(I've seen this before)
'also contains i understand' is the wordplay.
'also' becomes 'and' (both can mean in addition).
'contains' is an insertion indicator.
'understand' becomes 'see' (synonyms).
'i'+'see'='isee'
'and' going around 'isee' is 'ANISEED'.
(Other definitions for aniseed that I've seen before include "Licorice-like flavour" , "Aromatic flavouring" , "Plant" , "Strong flavour" , "Licorice-flavoured sweets" .)