One type of racing at venue for another — largely a shambles (6)
I believe the answer is:
fiasco
'a shambles' is the definition.
(I've seen this before)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for fiasco that I've seen before include "Sudden and complete collapse" , "Total debacle" , "bomb" , "Ignominious failure" , "Ignominious result" .)