A need is developing for fennel, perhaps (7)
I believe the answer is:
aniseed
'fennel perhaps' is the definition.
I can't tell whether this defines the answer.
'a need is developing' is the wordplay.
'developing' indicates anagramming the letters (letters developed into a new form).
'need'+'is'='needis'
'needis' anagrammed gives 'niseed'.
'a'+'niseed'='ANISEED'
'for' is the link.
Can you help me to learn more?
(Other definitions for aniseed that I've seen before include "Liquorice flavouring, used in cookery" , "Flavouring herb" , "Flavouring of e.g. absinthe" , "Liquorice flavour" , "Strong flavouring often used in sweets" .)