Tea served in a set (6)
I believe the answer is:
tisane
'tea' is the definition.
(I know that tisane is a type of herb tea)
'served in a set' is the wordplay.
'served' indicates an anagram.
'in'+'a'+'set'='inaset'
'inaset' is an anagram of 'TISANE'.
(Other definitions for tisane that I've seen before include "Herbal tea drink" , "Herb-tea" , "relaxing drink" , "Herb tea" , "Herbal infusion" .)