In shock, go back up for rabbit (6)
I believe the answer is:
jabber
'rabbit' is the definition.
(I know that rabbit can be written as jabber)
'in shock go back up' is the wordplay.
'in' indicates putting letters inside.
'shock' becomes 'jar' (I've seen this before).
'go back' becomes 'ebb' (I've seen this in another clue).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'ebb' in reverse letter order is 'bbe'.
'jar' going around 'bbe' is 'JABBER'.
'for' acts as a link.
(Other definitions for jabber that I've seen before include "One punching" , "rabbit?" , "Person giving injection" , "Talk rapidly/excitedly" , "Talk incessantly" .)