Outwardly a variety of leek, often boiled (6)
I believe the answer is:
kettle
'outwardly a variety of leek often boiled' is the definition.
I can't tell whether this defines the answer.
'outwardly a variety of leek often boiled' is the wordplay.
'outwardly' is an insertion indicator (some letters go on the outside).
'a variety of' indicates an anagram.
'often boiled' becomes 'tt' (I can't justify this - if you can you should believe this answer much more).
'leek' is an anagram of 'kele'.
'kele' going around 'tt' is 'KETTLE'.
Can you help me to learn more?
(Other definitions for kettle that I've seen before include "Vessel for heating liquids" , "The pot may call this black" , "A fence to catch fish" , "Spouted vessel" , "Container for heating 10" .)