Went back over grass, taking cart back (8)
I believe the answer is:
retraced
'went back' is the definition.
(retracing is a kind of going back)
'grass taking cart back' is the wordplay.
'grass' becomes 'reed' (type of grass plant).
'taking' is an insertion indicator.
'back' says the letters should be written backwards.
'cart' reversed gives 'trac'.
'reed' enclosing 'trac' is 'RETRACED'.
'over' acts as a link.
(Other definitions for retraced that I've seen before include "Followed back" , "Discovered" , "Once more found" .)