Went off thoroughly confused (6)
I believe the answer is:
addled
'thoroughly confused' is the definition.
(I've seen this in another clue)
'went' is the wordplay.
I cannot really see how this works, but
'went' could be 'led' ('lead' can be a synonym of 'go') and 'led' is found within the answer.
The remaining letters 'add' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'off' acts as a link.
Can you help me to learn more?
(Other definitions for addled that I've seen before include "Of egg, rotten and producing no chick" , "Corrupt" , "(Of an egg) went bad" , "Confused (wits); made rotten" , "Confused and vague" .)