Flavouring, I understand, goes in as well (7)
I believe the answer is:
aniseed
'flavouring' is the definition.
(I've seen this before)
'i understand goes in as well' is the wordplay.
'understand' becomes 'see' (synonyms).
'goes in' indicates putting letters inside.
'as well' becomes 'and' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'i'+'see'='isee'
'isee' going into 'and' is 'ANISEED'.
Can you help me to learn more?
(Other definitions for aniseed that I've seen before include "Flavouring herb" , "Liquorice flavour" , "Aromatic flavouring" , "Cake flavouring" , "Liquorice flavouring -- ie Danes (anag)" .)