Herbal tea in stock; it is an early starter (6)
I believe the answer is:
tisane
'herbal tea' is the definition.
(tisane is a kind of herbal tea)
'stock it is an early starter' is the wordplay.
'stock' says the answer is hidden in the clue (I've seen 'stocks' mean this).
'TISANE' is hidden within 'it is an early starter'.
'in' acts as a link.
(Other definitions for tisane that I've seen before include "Infusion of e.g. dried or fresh flowers or leaves" , "Herb-tea" , "Infusion (eg of herbs or flowers)" , "Herb tea" , "Herbal infusion" .)