Article on a girl (4)
I believe the answer is:
thea
'girl' is the definition.
'article on a' is the wordplay.
'article' becomes 'the' (the 'definite article' part of speech**).
'on' says to put letters next to each other.
'the'+'a'='THEA'
(Other definitions for thea that I've seen before include "... Girl" , "Plant" , "Girl's name, tea genus" , "evergreen shrubs?" , "Female name meaning 'goddess'" .)