Sweet basil and leek nearly prepared (7,4)
I believe the answer is:
aniseed ball
'sweet' is the definition.
(I've seen this before)
'basil and leek nearly prepared' is the wordplay.
'nearly' means to remove the last letter.
'prepared' indicates anagramming the letters.
'basil'+'and'+'leek'='basilandleek'
'basilandleek' with its final letter taken off is 'basilandlee'.
'basilandlee' anagrammed gives 'ANISEED BALL'.
(Other definitions for aniseed ball that I've seen before include "Flavoursome sweet" , "Pungent sweet" , "Strongly-flavoured sweet" .)