Order instant tea to begin with (4)
I believe the answer is:
sect
'order' is the definition.
(I've seen this in another clue)
'instant tea to begin with' is the wordplay.
'instant' becomes 'sec' (I've seen this in another clue).
'to begin with' suggests taking the first letters.
The first letter of 'tea' is 't'.
'sec'+'t'='SECT'
(Other definitions for sect that I've seen before include "Group, faction" , "Dissenting body" , "Religious splinter group" , "party" , "Cult group" .)