Back to front? The opposite, militarily! (7)
I believe the answer is:
retreat
'back' is the definition.
(thesaurus)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for retreat that I've seen before include "place for meditation" , "withdrawal" , "Withdraw from battle" , "Climb down" , "Tree rat (anag)" .)