Severe judge imprisons learner … (5)
I believe the answer is:
'severe' is the definition.
'judge imprisons learner' is the wordplay.
'judge' becomes 'beak' (**).
'imprisons' means one lot of letters goes inside another.
'learner' becomes 'l'.
'beak' going around 'l' is 'BLEAK'.
(Other definitions for bleak that I've seen before include "Exposed to the elements" , "Unpleasantly cold" , "Desolate, hopoeless" , "Stark" , "''... House'' (Dickens)" .)