An analogy is unfinished - common outside Paris (10)
I believe the answer is:
comparison
'an analogy' is the definition.
(I've seen this before)
'is unfinished common outside paris' is the wordplay.
I cannot really see how this works, but
'is' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for comparison that I've seen before include "distinction" , "Assessment of differences" , "Analogy; likeness" , "Process of identifying differences" , "Similarity" .)