The opposite (4,5)
I believe the answer is:
vice versa
'the opposite' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for vice versa that I've seen before include "The opposite (also applies)" , "back to front" , "With the order reversed" , "Revise a VC? (anag)" , "In reverse order" .)