Commercial with evil warning (6)
I believe the answer is:
advice
'warning' is the definition.
(thesaurus)
'commercial with evil' is the wordplay.
'commercial' becomes 'ad'.
'with' says to put letters next to each other.
'evil' becomes 'vice' (vice is a kind of evil).
'ad'+'vice'='ADVICE'
(Other definitions for advice that I've seen before include "Opinion given about what to do" , "Supposedly wise words" , "Recommendation for a course of action" , "Suggestion (invited or otherwise)" , "Supposed words of wisdom" .)