Greatest drink tried regularly with this writer (7)
I believe the answer is:
supreme
'greatest' is the definition.
(I've seen this before)
'drink tried regularly with this writer' is the wordplay.
'drink' becomes 'sup' (to sup is to drink).
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'with' says to put letters next to each other.
'this writer' becomes 'me' (the person who wrote the clues).
The alternate letters of 'tried' are 're'.
'sup'+'re'+'me'='SUPREME'
(Other definitions for supreme that I've seen before include "Crowning" , "Cardinal, foremost" , "topmost level" , "Chief" , "God" .)