Fleeting fragrance follows the final weathercock (10)
I believe the answer is:
evanescent
'fleeting' is the definition.
(I've seen this in another clue)
'fragrance follows the final weathercock' is the wordplay.
'fragrance' becomes 'scent' (synonyms).
'follows' is a charade indicator (letters next to each other).
'final' says to take the final letters.
'weathercock' becomes 'vane' (I've seen this in another clue).
The last letter of 'the' is 'e'.
'e'+'vane'='evane'
'scent' put after 'evane' is 'EVANESCENT'.
(Other definitions for evanescent that I've seen before include "evaporating slowly" , "Passing" , "slipping away" , "Fast-fading" , "Transient" .)