Detested running the ad (5)
I believe the answer is:
hated
'detested' is the definition.
('hate' can be a synonym of 'detest')
'running the ad' is the wordplay.
'running' indicates an anagram.
'the'+'ad'='thead'
'thead' anagrammed gives 'HATED'.
(Other definitions for hated that I've seen before include "Heartily disliked" , "Unpopular" , "Death (anag)" , "viewed with hostility" , "Despised" .)