Imprisonment having stolen university gown (5)
I believe the answer is:
dress
'gown' is the definition.
(gown is a kind of dress)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for dress that I've seen before include "changing gear" , "Straighten the line" , "clean > bandage" , "To prepare" , "Cultivate < tidy" .)