Failing to follow advertisement's counsel (6)
I believe the answer is:
advice
'counsel' is the definition.
(thesaurus)
'failing to follow advertisement's' is the wordplay.
'failing' becomes 'vice' (I've seen this in other clues).
'to follow' is a charade indicator (letters next to each other).
'advertisement' becomes 'ad' ('ad' can be a synonym of 'advertisement').
'vice' put after 'ad' is 'ADVICE'.
(Other definitions for advice that I've seen before include "Guidance; delivery note" , "Opinion given about what to do" , "tip" , "Counsel given" , "Admonition" .)