Rank as confidential (7)
I believe the answer is:
private
I believe this is a double definition.
'rank' is the first definition.
(I've seen this before)
'confidential' is the second definition.
(similar in meaning)
'as' is the link.
(Other definitions for private that I've seen before include "To most, unknown" , "Lowest rank of enlisted person" , "One's own" , "Lowest ranking soldier" , "Secret - soldier of the lowest rank" .)