One Barking prison given official documentation (5)
I believe the answer is:
canid
'one barking' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'prison given official documentation' is the wordplay.
'prison' becomes 'can' (the can is American slang for prison).
'given' is a charade indicator (letters next to each other).
'official documentation' becomes 'id' (identification documents. I am not sure about the 'official' bit.).
'can'+'id'='CANID'
Can you help me to learn more?
(Another definition for canid that I've seen is " dog maybe".)