Prison housing one murderer (4)
I believe the answer is:
cain
'murderer' is the definition.
(Biblical figure)
'prison housing one' is the wordplay.
'prison' becomes 'can' (the can is American slang for prison).
'housing' is an insertion indicator.
'one' becomes 'i' (Roman numeral).
'can' enclosing 'i' is 'CAIN'.
(Other definitions for cain that I've seen before include "Eve's firstborn" , "First murderer reported in the Bible" , "Eldest son of Adam, Eve" , "Abel's brother" , "Biblical killer" .)