Calm after student finds rent (5)
I believe the answer is:
lease
'rent' is the definition.
(thesaurus)
'calm after student' is the wordplay.
'calm' becomes 'ease' (I've seen this before**).
'after' says to put letters next to each other.
'student' becomes 'l' (as in L-plates for learner drivers).
'ease' after 'l' is 'LEASE'.
'finds' acts as a link.
(Other definitions for lease that I've seen before include "Property rental agreement" , "Tenancy contract" , "Let out, hire" , "Term of a rental contract" , "Let; rent" .)