Take offence at harness (6)
I believe the answer is:
bridle
I believe this is a double definition.
'take offence' is the first definition.
(I've seen this before)
'harness' is the second definition.
(thesaurus)
'at' is the link.
(Other definitions for bridle that I've seen before include "Show indignation" , "Part of horse's headgear" , "Restrain" , "Become indignant" , "Check" .)