A writer put in prison (3)
I believe the answer is:
pen
This clue might be a double definition.
'a writer' is the first definition.
(something which writes)
'in prison' is the second definition.
'pen' can be an answer for 'prison' (both can mean an enclosure). I am unsure of the 'in' bit.
'put' is the link.
Can you help me to learn more?
(Other definitions for pen that I've seen before include "Cage - bird" , "Shut up" , "Small enclosure" , "Pound" , "dash off" .)