Student leaving form makes you sore (4)
I believe the answer is:
stye
'sore' is the definition.
(I've seen this before)
'student leaving form' is the wordplay.
'student' becomes 'l' (as in L-plates for learner drivers).
'leaving' is a deletion indicator.
'form' becomes 'style' (style is a kind of form).
'style' with 'l' taken away is 'STYE'.
'makes you' acts as a link.
(Other definitions for stye that I've seen before include "pain for the observer" , "Eye problem" , "irritation to the viewer" , "Infected swelling of the eye" , "Climb" .)