The bar Ron trashed is disgusting (9)
I believe the answer is:
abhorrent
'is disgusting' is the definition.
(I've seen this before)
'the bar ron trashed' is the wordplay.
'trashed' indicates an anagram.
'the'+'bar'+'ron'='thebarron'
'thebarron' with letters rearranged gives 'ABHORRENT'.
(Other definitions for abhorrent that I've seen before include "noisome" , "Repulsive" , "Hated" , "Inspiring disgust and loathing" , "far from agreeable" .)