Herbs and spices -- a sign one's cooking (9)
I believe the answer is:
seasoning
'herbs and spices' is the definition.
(herbs and spices are used to season food)
'a sign one's cooking' is the wordplay.
'cooking' indicates an anagram (letters cooked up into a new form).
'a'+'sign'+'ones'='asignones'
'asignones' with letters rearranged gives 'SEASONING'.
(Other definitions for seasoning that I've seen before include "Salt, pepper, herbs etc added to food" , "Add it to give flavour" , "Could be salt" , "Salt, possibly" , "Relish" .)