Ages wasted on flavouring (4)
I believe the answer is:
sage
'flavouring' is the definition.
(sage is a kind of flavouring)
'ages wasted' is the wordplay.
'wasted' indicates anagramming the letters.
'ages' anagrammed gives 'SAGE'.
'on' is the link.
(Other definitions for sage that I've seen before include "Herb; wise person" , "Profoundly wise" , "Learned" , "___ and onion" , "Wise green herb?" .)