Officer reversed in Lada crossing border (7)
I believe the answer is:
admiral
'officer' is the definition.
(admiral is a kind of officer)
'reversed in lada crossing border' is the wordplay.
'reversed' says the letters should be written in reverse.
'in' means one lot of letters goes inside another.
'crossing border' becomes 'rim' (both can mean an edge. I am not sure about the 'crossing' bit.).
'lada' enclosing 'rim' is 'larimda'.
'larimda' back-to-front is 'ADMIRAL'.
Can you help me to learn more?
(Other definitions for admiral that I've seen before include "Naval officer of high rank" , "High-ranking naval officer like Nelson" , "Blake, for one" , "Chief commander of fleet" , "Naval high-up" .)