Dullness unacceptable between physician and his number three (8)
I believe the answer is:
monotony
'dullness' is the definition.
The definition and answer can be both human attributes as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'unacceptable between physician and his number three' is the wordplay.
I cannot really see how this works, but
'unacceptable' could be 'noton' (I've seen this before) and 'noton' is present in the answer.
'number' could be 'm' (M is an example) and 'm' is present in the answer.
The remaining letters 'oy' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for monotony that I've seen before include "Tedious lack of variety" , "Lack of excitement" , "boring routine" , "Tediousness" , "It's wearisome" .)