There's nothing persistent in this scent (5)

I believe the answer is:

odour

I'm a little stuck... Click here to teach me more about this clue!

'this scent' is the definition.
(synonyms)

'there's nothing persistent' is the wordplay.
'there's nothing' becomes 'o' (I've seen this in other clues).
'persistent' becomes 'dour' (I can't justify this - if you can you should believe this answer much more).
'o'+'dour'='ODOUR'

'in' is the link.

Can you help me to learn more?

(Other definitions for odour that I've seen before include "Any property detected by the olfactory system" , "Nasty smell" , "Olfactory sensation" , "for the nose to detect" , "Pong" .)

I've seen this clue in The Irish Independent and The Globe and Mail.

Want a hint initially instead of a full solution? Install my app