A need is developing for flavour (7)
I believe the answer is:
aniseed
'for flavour' is the definition.
(I've seen this before)
'a need is developing' is the wordplay.
'developing' indicates anagramming the letters (letters developed into a new form).
'need'+'is'='needis'
'needis' with letters rearranged gives 'niseed'.
'a'+'niseed'='ANISEED'
(Other definitions for aniseed that I've seen before include "Natural flavouring" , "Liquorice flavouring, used in cookery" , "Strong flavouring often used in sweets" , "Flavouring in pastis" , "Licorice-flavoured sweets" .)