Plant list newly included in article (7)
I believe the answer is:
thistle
'plant' is the definition.
(thistle is a kind of plant)
'list newly included in article' is the wordplay.
'newly' indicates anagramming the letters.
'included in' means one lot of letters goes inside another.
'article' becomes 'the' (the 'definite article' part of speech).
'list' with letters rearranged gives 'istl'.
'istl' going inside 'the' is 'THISTLE'.
(Other definitions for thistle that I've seen before include "Lithest kind of prickly plant" , "Scotland's emblem" , "that blows down when it's windy" , "The list includes Scottish emblem" , "Lithest (anag) - plant" .)