Go back?; Just the opposite! (7)
I believe the answer is:
reverse
This clue might be a double definition.
'go back?' is the first definition.
(I've seen this before)
'the opposite' is the second definition.
('reverse' can be a synonym of 'opposite')
'just' is the link.
I am not very happy about this link. It may belong to one of the definitions.
Can you help me to learn more?
(Other definitions for reverse that I've seen before include "Go backwards" , "Britannia's place" , "Move backwards" , "Upset" , "A defeat to go backward" .)