Dennis sadly offended (6)
I believe the answer is:
sinned
'offended' is the definition.
Although both the answer and definition are past participle verbs, I don't see how they can define each other.
'dennis sadly' is the wordplay.
'sadly' indicates an anagram.
'dennis' with letters rearranged gives 'SINNED'.
Can you help me to learn more?
(Other definitions for sinned that I've seen before include "was wicked" , "trespassed" , "Send in (anag.)" , "Transgressed the moral law" , "Committed a serious offence" .)