Raise student by one foot (4)
I believe the answer is:
lift
'raise' is the definition.
(lifting is a kind of raising)
'student by one foot' is the wordplay.
'student' becomes 'l' (as in L-plates for learner drivers).
'by' says to put letters next to each other.
'one' becomes 'I' (Roman numeral).
'foot' becomes 'ft' (synonyms).
'l'+'i'+'ft'='LIFT'
(Other definitions for lift that I've seen before include "Raise - shot in the arm" , "Raise; elevator" , "Pick up" , "Steal (colloq.); elevator" , "It's an elevator in USA" .)