Outstanding Parisian's an entertaining fellow (6)
I believe the answer is:
undone
'outstanding' is the definition.
Both the definition and answer are adjectives. Maybe there's a link between them I don't understand?
'parisian's an entertaining fellow' is the wordplay.
'parisian' becomes 'une' (I can't explain this - if you can you should give a lot more credence to this answer).
'an entertaining' means one lot of letters goes inside another.
'fellow' becomes 'don' (I've seen this before).
'une' going around 'don' is 'UNDONE'.
Can you help me to learn more?
(Other definitions for undone that I've seen before include "Reversed" , "Not bound" , "Opened" , "Unfastened or brought to ruin" , "Not finished; untied" .)