Tea primarily is an English infusion (6)
I believe the answer is:
tisane
'infusion' is the definition.
(I've seen this before)
'tea primarily is an english' is the wordplay.
'primarily' suggests taking the first letters.
'english' becomes 'e' (abbreviation).
The initial letter of 'tea' is 't'.
't'+'is'+'an'+'e'='TISANE'
(Other definitions for tisane that I've seen before include "Herb-tea" , "brew" , "Herbal tea drink" , "Herbal infusion" , "Herb tea" .)