Controversial hotel ad is detested (7)
I believe the answer is:
loathed
'is detested' is the definition.
(I've seen this in another clue)
'controversial hotel ad' is the wordplay.
'controversial' indicates anagramming the letters.
'hotel'+'ad'='hotelad'
'hotelad' anagrammed gives 'LOATHED'.
(Other definitions for loathed that I've seen before include "Hated" , "Cordially detested" , "Detested and abominated" , "'Abhorred, detested (7)'" , "Regarded with disgust and hatred" .)