Cart reversed into quad (4)
I believe the answer is:
yard
'quad' is the definition.
(thesaurus)
'cart reversed' is the wordplay.
'cart' becomes 'dray' (a cart without sides for delivering heavy loads).
'reversed' is a reversal indicator.
'dray' in reverse letter order is 'YARD'.
'into' is the link.
(Other definitions for yard that I've seen before include "Tract of land enclosed for a particular purpose" , "Police" , "3 feet" , "Enclosed area by building - old measure" , "A little under a metre" .)