In US law officer, it reflects rank (5)
I believe the answer is:
fetid
'rank' is the definition.
(I've seen this before)
'in us law officer it reflects' is the wordplay.
'in' indicates putting letters inside.
'us law officer' becomes 'def' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'reflects' says the letters should be written backwards.
'def' placed around 'it' is 'ditef'.
'ditef' in reverse letter order is 'FETID'.
Can you help me to learn more?
(Other definitions for fetid that I've seen before include "Putrid and stinking" , "Foul-smelling or stinking" , "Smelling bad, stinking" , "Stinking or foul, could be bad breath" , "Stinking, perhaps breath" .)