Smells, on reflection, concealing a flavour (6)
I believe the answer is:
season
'flavour' is the definition.
(I know that flavour can be written as season)
'smells on reflection concealing a' is the wordplay.
'smells' becomes 'noses' (nosing is a kind of smelling).
'on reflection' says the letters should be written in reverse.
'concealing' indicates putting letters inside.
'noses' reversed gives 'seson'.
'seson' placed around 'a' is 'SEASON'.
(Other definitions for season that I've seen before include "Spring, say" , "Major division of year characterised by weather and growth" , "Add flavourings" , "Add salt, pepper, spice etc" , "eg.Summer" .)