Alternatively, gone off with a flavouring (7)
I believe the answer is:
oregano
'flavouring' is the definition.
(oregano is a kind of flavouring)
'alternatively gone off with a' is the wordplay.
'alternatively' becomes 'or'.
'off with' is an anagram indicator.
'gone' mixed up with 'a' gives 'egano'.
'or'+'egano'='OREGANO'
(Other definitions for oregano that I've seen before include "Herb related to marjoram" , "food flavouring" , "part of Mediterranean diet?" , "Mediterranean herb" , "leaves for season" .)