Ring pulled back and forth (6)
I believe the answer is:
'forth' is the definition.
('onward' can be a synonym of 'forth')
'ring pulled back' is the wordplay.
'ring' becomes 'o'.
'pulled' becomes 'drawn' (drawing is a kind of pulling).
'back' says the letters should be written in reverse.
'drawn' backwards is 'nward'.
'and' is the link.
(Other definitions for onward that I've seen before include "Advanced" , "In a forward direction" , "Direction to be taken by Christian soldiers?" , "Ahead" , "In front" .)