Warn maid with nosh cooked (8)
I believe the answer is:
admonish
'warn' is the definition.
(I know that warn can be written as admonish)
'maid with nosh cooked' is the wordplay.
'with' is a charade indicator (letters next to each other).
'cooked' indicates an anagram (letters cooked into a new form).
'maid' put after 'nosh' is 'noshmaid'.
'noshmaid' is an anagram of 'ADMONISH'.
(Other definitions for admonish that I've seen before include "Scold, wag the finger at" , "censure" , "Gently reprove" , "criticise" , "Warn sternly" .)