Being in the red is rotten, not well spoken of (7)
I believe the answer is:
reviled
'well spoken of' is the definition.
Both the definition and answer are adjectives. Perhaps you can see an association between them that I can't see?
'being in the red is rotten' is the wordplay.
'being in the' is an insertion indicator.
'is rotten' becomes 'evil' (I've seen this in another clue).
'red' enclosing 'evil' is 'REVILED'.
'not' is the link.
Can you help me to learn more?
(Other definitions for reviled that I've seen before include "Maligned, vilified" , "Deliver (anag.)" , "Abused" , "Abusively criticised" .)