Season well, including new thyme — explain recipe for starters (6)
I believe the answer is:
winter
'season' is the definition.
(winter is a season)
'well including new thyme explain recipe for starters' is the wordplay.
'for starters' says to take the initial letters.
The first letters of 'well including new thyme explain recipe' is 'WINTER'.
(Other definitions for winter that I've seen before include "Coldest season" , "'Now is the . . . . . . of our discontent' (Richard III)" , "period of discontent?" , "'If . . . . . . comes, can spring be far behind?'" , "Cold season" .)