Why is King Edward initially included to produce drink (7)
I believe the answer is:
whiskey
'drink' is the definition.
(whiskey is a kind of drink)
'why is king edward initially included' is the wordplay.
'initially' suggests taking the first letters.
'included' means one lot of letters goes inside another.
The first letters of 'king edward' is 'ke'.
'is'+'ke'='iske'
'why' enclosing 'iske' is 'WHISKEY'.
'to produce' acts as a link.
(Other definitions for whiskey that I've seen before include "Irish drink" , "Irish spirit" , "Irish or American liquor" .)