Butterfly down stalk (11)

I believe the answer is:

swallowtail

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'butterfly' is the definition.
(I've seen this before)

'down stalk' is the wordplay.
'down' becomes 'swallow' (both can mean to consume or eat).
'stalk' becomes 'tail' (I am not sure about this - if you are sure you should believe this answer much more).
'swallow'+'tail'='SWALLOWTAIL'

Can you help me to learn more?

(Other definitions for swallowtail that I've seen before include "Butterfly" , "coat" , "In circle, mythical snake does" , "insect" .)

I've seen this clue in The Telegraph.

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