Girl with New York student's material (5)
I believe the answer is:
vinyl
'material' is the definition.
(I know that vinyl is a type of material)
'girl with new york student's' is the wordplay.
'girl' becomes 'Vi' (short for Violet).
'with' is a charade indicator (letters next to each other).
'new york' becomes 'ny'.
'student' becomes 'l' (as in L-plates for learner drivers).
'vi'+'ny'+'l'='VINYL'
(Other definitions for vinyl that I've seen before include "PVC" , "A plastic (LPs)" , "LP material" , "Old record material" , "Synthetic polymer" .)