Younger or lower in rank (6)
I believe the answer is:
junior
I believe this is a double definition.
'younger' is the first definition.
(I've seen this before)
'lower in rank' is the second definition.
(I've seen this in another clue)
(Other definitions for junior that I've seen before include "Younger or lower in rank" , "Inferior in rank, son" , "Low in status or rank" , "Younger - subordinate" , "Lower in rank, son" .)