Is consumed by a requirement for herbal product (7)
I believe the answer is:
aniseed
'herbal product' is the definition.
(seed of anise, a herb)
'is consumed by a requirement' is the wordplay.
'consumed by' means one lot of letters goes inside another (inserted letters get consumed).
'requirement' becomes 'need' (synonyms).
'a'+'need'='aneed'
'is' placed inside 'aneed' is 'ANISEED'.
'for' is the link.
(Other definitions for aniseed that I've seen before include "Strong flavour" , "Flavouring in pastis" , "Licorice-flavoured sweets" , "Die sane (anag)" , "Plant" .)