A shade less than well (3-6)
I believe the answer is:
'well' is the definition.
Both the answer and definition are adjectives.
Maybe you can see an association between them that I don't see?
'a shade less than' is the wordplay.
I cannot really understand how this works, but
'shade' could be 'colour' (I've seen this before) and 'colour' is located in the answer.
The remaining letters 'off' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for off-colour that I've seen before include "Unwell or mildly indecent" , "Unwell or indelicate - a bit pale?" , "Not in the pink?" , "Unwell -- risque" , "Out of sorts" .)