Produce fresh green tea (8)
'produce' is the definition.
(generating is a kind of producing)
'fresh green tea' is the wordplay.
'fresh' is an anagram indicator.
'greentea' with letters rearranged gives 'GENERATE'.
(Other definitions for generate that I've seen before include "Produce, electricity say", "Produce (energy, etc)", "evolve", "Produce, create", "Make".)