Go over in box cart? (8)
I believe the answer is:
rehearse
'go over' is the definition.
(thesaurus)
'in box cart?' is the wordplay.
'in' becomes 're' (I can't explain this - if you can you should give a lot more credence to this answer).
'box cart?' becomes 'hearse' (cart for carrying coffins or 'boxes').
're'+'hearse'='REHEARSE'
(Other definitions for rehearse that I've seen before include "Recite - try out" , "Prepare for a stage production" , "Practise - run through" , "Practise like actor" , "Practise (one's lines)" .)