Imprisoned right person with secret information (7)
I believe the answer is:
insider
'person with secret information' is the definition.
'imprisoned right' is the wordplay.
'imprisoned' becomes 'inside' (I've seen this before).
'right' becomes 'r' (common abbreviation).
'inside'+'r'='INSIDER'
(Other definitions for insider that I've seen before include "One privy to info by being within organisation" , "One of us" , "person with confidential info" , "Accepted member of accepted group, has access to information" , "Member of clique" .)