Unfilled post in Virginia prison extremely cushy (7)
I believe the answer is:
vacancy
'unfilled post' is the definition.
'vacancy' can be an answer for 'post' (I have seen 'Unoccupied post ' mean 'vacancy' so perhaps 'post' could also mean 'vacancy'). I am not sure about the 'unfilled' bit.
'virginia prison extremely cushy' is the wordplay.
'virginia' becomes 'va' (US state abbreviation).
'prison' becomes 'can' (the can is American slang for prison).
'extremely' suggests removing the centre (only the extremes of the word are used).
'cushy' with its centre removed is 'cy'.
'va'+'can'+'cy'='VACANCY'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for vacancy that I've seen before include "Unoccupied situation" , "Unoccupied post" , "Unoccupied state, job or apartment" , "Opportunity" , "An opening, job or apartment" .)