Season, say, with a herb (5)
I believe the answer is:
thyme
'herb' is the definition.
(I know that thyme is a type of herb)
'season say' is the wordplay.
'season' becomes 'time' (both can mean a period).
'say' indicates a 'sounds like' (homophone) clue.
'time' is a homophone of 'THYME'.
'with a' is the link.
(Other definitions for thyme that I've seen before include "Kind of mint" , "something fragrant?" , "Ingredient in cooking" , "Small shrub: leaves used to season food" , "Culinary herb of the mint family" .)