Young girl soundly curses English student (6)
I believe the answer is:
damsel
'young girl' is the definition.
(I've seen this before)
'soundly curses english student' is the wordplay.
'soundly' shows a homophone (sound like).
'curses' becomes 'damns' ('damn' can be a synonym of 'curse').
'english' becomes 'e' (abbreviation).
'student' becomes 'l'.
'damns' is a homophone of 'dams'.
'dams'+'e'+'l'='DAMSEL'
(Other definitions for damsel that I've seen before include "Old-fashioned young woman" , "Girl - type of fly" , "Maid" , "Young lady of old, perhaps in distress" , "Girl (literary)" .)