Students have to copy jacket part (5)
I believe the answer is:
lapel
'jacket part' is the definition.
(I've seen this in another clue)
'students have to copy' is the wordplay.
'students' becomes 'LL' (an abbreviation for learner driver written twice).
'have' indicates putting letters inside.
'to copy' becomes 'ape' (ape can mean to copy or imitate).
'll' enclosing 'ape' is 'LAPEL'.
(Other definitions for lapel that I've seen before include "Jacket fold" , "top of coat" , "Feature of a jacket" , "Revere on a coat" , "Extended part of a collar" .)