Vice apt to corrupt prisoner (7)
I believe the answer is:
captive
'prisoner' is the definition.
(I know that prisoner can be written as captive)
'vice apt to corrupt' is the wordplay.
'to corrupt' indicates anagramming the letters (a corrupted spelling of the word).
'vice'+'apt'='viceapt'
'viceapt' anagrammed gives 'CAPTIVE'.
(Other definitions for captive that I've seen before include "Detainee" , "Prisoner" .)