Sweet-smelling returning salesperson seethed (8)
I believe the answer is:
perfumed
'sweet-smelling' is the definition.
(synonyms)
'returning salesperson seethed' is the wordplay.
'returning' shows that the letters should be reversed in order.
'salesperson' becomes 'rep' (sales rep).
'seethed' becomes 'fumed' (I've seen this in another clue).
'rep' reversed gives 'per'.
'per'+'fumed'='PERFUMED'
(Other definitions for perfumed that I've seen before include "tempting aroma" , "Scented pp" , "Fragrant" , "With a natural fragrance" .)