Let go, student I rebuked (9)
I believe the answer is:
liberated
'let go' is the definition.
'student i rebuked' is the wordplay.
'student' becomes 'l' (as in L-plates for learner drivers).
'rebuked' becomes 'berated' ('berate' can be a synonym of 'rebuke').
'l'+'i'+'berated'='LIBERATED'
(Other definitions for liberated that I've seen before include "Released" , "Freed from social conventions" , "Free" , "Emancipated" , "Having stolen" .)