A French prison on the outskirts of Nancy -- that's weird (7)
I believe the answer is:
uncanny
'weird' is the definition.
('uncanny' can be a synonym of 'weird')
'a french prison on the outskirts of nancy' is the wordplay.
'a french' becomes 'un' ('a' in French).
'prison' becomes 'can' (the can is American slang for prison).
'on' says to put letters next to each other.
'the outskirts of' suggests removing the centre.
'nancy' with its middle taken out is 'ny'.
'un'+'can'+'ny'='UNCANNY'
'that's' acts as a link.
(Other definitions for uncanny that I've seen before include "Weird, unnatural" , "Weird; supernatural" , "Extraordinary, beyond what is normal" , "Incredible" , "Eerie" .)