Smells arising from cheeses once (5)
I believe the answer is:
noses
'smells' is the definition.
(nosing is a kind of smelling)
'arising from cheeses once' is the wordplay.
'arising' shows that the letters should be reversed in order.
'from' says the answer is hidden in the clue.
'seson' is hidden in the letters of 'cheeses once'.
'seson' written backwards gives 'NOSES'.
(Other definitions for noses that I've seen before include "Hooters" , "Olfactory organs" , "Proboscises" , "Beaks, conks" , "Pries" .)