Girl, English, posh, lovely (6)
I believe the answer is:
eunice
'girl' is the definition.
'english posh lovely' is the wordplay.
'english' becomes 'e' (abbreviation).
'posh' becomes 'u' (abbreviation for upper-class - opposite to non-u).
'lovely' becomes 'nice' (I've seen this before).
'e'+'u'+'nice'='EUNICE'
(Other definitions for eunice that I've seen before include "Female name deriving from happy victory in Greek" , "Woman" , "Girl's name" , "Girl" .)