Student always has a jemmy (5)
I believe the answer is:
lever
'a jemmy' is the definition.
(I've seen this before)
'student always' is the wordplay.
'student' becomes 'l' (as in L-plates for learner drivers).
'always' becomes 'ever' (synonyms).
'l'+'ever'='LEVER'
'has' acts as a link.
(Other definitions for lever that I've seen before include "Purchase from bar" , "Means of exerting force" , "Jemmy" , "Heavy bar" , "Rigid bar pivoted about a fulcrum" .)