Decline of French perfume (7)
I believe the answer is:
descent
'decline' is the definition.
(I know that decline can be written as descent)
'of french perfume' is the wordplay.
'of french' becomes 'de' ('of' in French).
'perfume' becomes 'scent' (synonyms).
'de'+'scent'='DESCENT'
(Other definitions for descent that I've seen before include "Drop" , "Comedown (of ancestry?)" , "Roots" , "Slope leading from top" , "Downward path" .)