Obsession is wrong over eating French bread (8)
I believe the answer is:
neurosis
'obsession' is the definition.
(I've seen this before)
'wrong over eating french bread' is the wordplay.
'wrong' becomes 'sin' (wrong can mean a sin or crime).
'over' says the letters should be written backwards.
'eating' indicates putting letters inside.
'french bread' becomes 'euros' (I've seen this in another clue).
'sin' written backwards gives 'nis'.
'nis' enclosing 'euros' is 'NEUROSIS'.
'is' is the link.
(Other definitions for neurosis that I've seen before include "Mild mental illness not caused by an organic disease" , "Obsession" , "Mental disorder of resinous origin" , "Trouble in mind" , "Mild mental condition" .)