Rescue student in dressing (5)
I believe the answer is:
salve
'dressing' is the definition.
(thesaurus)
'rescue student in' is the wordplay.
'rescue' becomes 'save' (saving is a kind of rescuing).
'student' becomes 'l' (as in L-plates for learner drivers).
'in' means one lot of letters goes inside another.
'save' placed around 'l' is 'SALVE'.
(Other definitions for salve that I've seen before include "Soothing ointment - may also be applied to feelings" , "Vales (anag.)" , "Soothing cream" , "Ointment for wounds" , "Healing ointment" .)