So old amour turned out not to be the most fragrant (10)
I believe the answer is:
malodorous
'fragrant' is the definition.
(thesaurus)
'so old amour turned out' is the wordplay.
'turned out' indicates an anagram (turn out can mean to organise).
'so'+'old'+'amour'='sooldamour'
'sooldamour' with letters rearranged gives 'MALODOROUS'.
'not to be the most' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for malodorous that I've seen before include "Foul-smelling" , "Having a bad smell" , "Smelling very unpleasant" .)