Gold, sir, returns fragrance (5)
I believe the answer is:
orris
'fragrance' is the definition.
'gold sir returns' is the wordplay.
'gold' becomes 'or' ('or' is the heraldic name for gold).
'returns' says the letters should be written backwards.
'sir' written backwards gives 'ris'.
'or'+'ris'='ORRIS'
(Other definitions for orris that I've seen before include "Fragrant iris extract" , "Plant rhizome used in perfumery" , "Source of perfume" , "Scent from iris rhizome" , "Flag" .)